@Starswirl  
There also the impact of their actions versus their longevity.  
Discord: IMMORTAL reality bender on recorded rampage on Equestria that just ESCAPED the prison intended for him. If we don’t reform him it will happen again. Because we did try emprisonment.  
Starlight: mortal who bent space and time for revenge according to three people. Also held a town hostage by their cutie mark, but no one pressed charges. So have a social workers on her case.  
Cozy Glow: mortal kid with a warped world view a manipulative streak and a consumate liard conspire with known fellon and find a way to syphon the magic out of the world and does it, not out of scorn by to fullfill her ambition’s path, before her plan get reversed. Lifetime imprisonment because she could do it again

Ah! But the thing is Cozy Glow plan was reverted while Starlight Glimmer was Averted thus while only Twilight and Spike report to have suffered in other timelines every creature on the globe had to deal with magic being gone.

next season? :’v

@Copper Knight  
Still feigning an apology would’ve probably worked

@Copper Knight  

 
Cozy deserves an Oscar for her acting.

@PaintEdits  
She actually did retreat to her nice persona but was busted right off the bat. The Student Six and Starlight already knew the truth.

@Copper Knight  
“You sort of need to fill in facts that aren’t there.” In many judicial systems, children are not held to the same standard as adults and you don’t always have all the facts as I mentioned earlier.
 
 
@Copper Knight  

 
Did you read my comments? I said some are not, and some are. Here I’ll quote myself.
 
@PaintEdits  

 
You’re making a lot of presumptions and statements that straight up conflict with comments I’ve made stating otherwise. Ironic @Copper Knight  

 
I’m perfectly aware what she did and her lack of remorse.
 
Your angle is intent, mine is a child’s brain can in many cases, not be developed/warped due to external factors beyond her control. I’m simply stating she didn’t deserve tartarus, if anything a minimum security prison.
 
Also, I’ve read Lord of the Flies (don’t assume, it makes an “ass” out of “u” and “me”). And I believe things could easily turn that way precisely because morality can be underdeveloped in you guessed it, youth.
 
Just some food for thought if she were REALLY smart, why wouldn’t she retreat to her goody two shoes facade and feign remorse to avoid prison and have a much easier time with her next evil plan?

@Starswirl
 
I bet you if she’d appeared apologetic, they would’ve accepted her.

Here’s the reason Cozy Glow wasn’t easily forgiven: She’s not a powerful spellcaster.
 
Discord? Powerful.  
Starlight? Powerful.
 
They said as much. So, the reason might be… rather cynical.

@PaintEdits  
The problem with your argument is that you are trying to fill facts that are not there. She was point blank asked why she would do this by Twilight and Cozy said power and was rather adamant that since it didn’t work out there, she could do it somewhere else.
 
FURTHERMORE, children are not as stupid as you think. There are particularly nasty children and teenagers out there. Not from abusive homes or not instilled with a wrong sense of morality. Just plain evil and thinking otherwise is very foolish.
 
I don’t think you really realize what Cozy did in this finale. She attempted murder via Cloudsdale (she knew magic would fail and made sure that field trip happened on time; they were saved because Rainbow has the reflexes to react in this situation), she trapped seven of the greatest heroes in Tartarus and hoped it was permanent, trapped another hero in something that will forever send her to another dimension, tried to remove the very lifeblood of the world (it’s safe to say, Celestia’s magic was used up and could no longer raise the sun causing eternal night and they had no magic to preserve foodstuffs and plants either), locked up a government official, planned to overthrow the rest of the government, tried to get rid of the Student Six and push racism to further her goals of manipulation, contacted one of the worst villains ever in the hope of learning stuff from him after seeing the horrible things he did, manipulated several ponies by using one of the core foundations of their society (friendship), and when backed in a corner, threatened to do it again elsewhere.
 
These are not the acts of a fool. Hell, Cozy Glow was at a school for friendship and learned all the same lessons that everyone else in the school learned. She had friends - the Mane Six liked her, the student body liked her, and the CMC were explicitly her friend. She had a really good position at the school.
 
Chrysilis escaped - most of them probably too tired to chase after her considering the transformation and the rest coming out of their pods. No one has said to reform her since and she was never encountered by the main cast in the Mean Six.
 
Discord was released because Celestia believed she could get a use out of him. Period. And, of course, that was after a thousand years imprisoned in stone and then a season in half being trapped again. And, Fluttershy figured out he was lonely and used that to keep him on a leash until the Tirek bit finally changed him completely.
 
That wouldn’t work on Cozy because she had everything except ruling Equestria.
 
But, seriously, read Lord of the Flies.

@PaintEdits  
Well, in that case, it’s been a pleasure discussing this with you!
 
As for the court document I linked, it’s actually about the Supreme Court decision that a minor cannot be given a life sentence without parole for a non-murder (it’s 84 pages, so I would definitely advise some skimming here and there). I mostly read up on it to make sure I wasn’t giving out bogus information.

@noradtwo  
I don’t feel badgered at all, I’m open to arguments that’d prove otherwise (granted my personal opinion is rather adamant here - and please don’t get me wrong, I don’t think every child that murders is some innocent that doesn’t know any better.) I’ll be sure to give that a read and it might open my perspective a bit. Thanks!

@PaintEdits  
I’m seeing that you feel strongly about this because of Cozy being a child. So I won’t badger you anymore after this.
 
At any rate, in real life, a minor tried as a minor can get a couple years in juvenile jail for a single attempted homicide. Cozy has (counts on fingers…) a lot of attempted homicides to her name. Also at least one count of treason. If the crime is severe enough (even for non-murder), minors can be given life sentences, though usually not without parole (So, again, I advise patience: who’s to say Twilight isn’t working on a plan, already?). And though precedent is a very important factor when a court makes a ruling, precedents can be overturned.
 
Note that I took most of this from Supreme Court rulings from the United States (obviously other countries do things differently, some for better, some for worse).
 
At any rate you can read about it here:
 
https://www.supremecourt.gov/opinions/09pdf/08-7412.pdf

@FanOfMostEverything  
Or she could stay there until the finale, having set up a back-up plan beforehoof. But yours is more likely, yeah.

@gingerninja666  
Again, age discrepancy. Your arguments would be more sound if Cozy was fully matured. She’s a child. There exist countless cases of children who murder their parents because they have not developed a sense of morality and thus, don’t (at least fully) realize the ramifications of their actions/that they’re even wrong. The fact Cozy is completely unremorseful is a testament to this.
 
A case in Poland a child killed his mother in his sleep because he was dared to. Another in Canada a child tried to murder both his parents because another kid said he’d let him bite off his penis if he did (I’m not kidding). Any digging on the internet will show you children who’ve shot their parents or a child at school that was bullying them. But they’re not jailed and (while I’m not saying all aren’t evil) many grow up to be normal, realize their actions and never kill again.
 
I don’t even like Cozy, I’m just saying that this sentence is totally asinine. Is her chance at reformation dashed because unlike Discord Celestia won’t be able to make any use of him?
 
@noradtwo
 
Discord’s centuries old and had a previous conviction.  
A maximum security prison is still overboard for Cozy.  
Last point I’m just arguing precedent. Valid question though, she should’ve been thrown in Tartarus.

@PaintEdits
 
You could read the situation with Chrys as them not wanting to make that mistake again with Cozy. She tried to run away, and they didn’t let it happen.
 
With Discord, there was a cynical reason when they first tried to reform him. Celestia thought he’d be useful. Once they started though, they quickly learned that all he really wanted was a friend. Someone to show him kindness and compassion. That… doesn’t really apply to Cozy. She was already a friendship student. She’d spent months learning how to be a good friend. She already had plenty of people who cared about her, who were willing to be selfless in support of her. So she’s not really like Discord.

@PaintEdits  
It was a season and a half before Celestia was ready to give Discord a chance to reform, and that was only with the insurance of the Elements ready to blast him (until Fluttershy made her gamble, at any rate). I advise patience.
 
At any rate, though we like to make jokes about “literal pony hell,” Tartarus has shown to be more of a maximum security prison with sweet interior design rather than the original, mythological Tartarus. And prison is a good place for someone who would have happily watched dozens of children die to achieve her goals. Plus the ultimate Equestrian crime: she wasn’t even a little regretful of her actions.
 
As for Chrysalis, I think the argument is easily flipped on its head: why didn’t they capture Chrysalis and lock her up like Tirek and Cozy?

@FanOfMostEverything
 
I’m sure she’ll be like Dr. Deviso in Supermansion and have a highly elaborate escape plan in place.

If Cozy doesn’t break out during the Season 9 premiere, I will be flat-out astonished.

@genervt  
You skipped my argument. Chrysalis and Discord both understood their actions very well and were what I consider adults.  
On top of this both of them are repeat offenders, yet Chrysalis was allowed to flee and Discord was given a chance to reform.  
Why do adult repeat offenders get off, but a youth first time offender, even if unapologetic, gets sent to hell?
 
 
@RIG  
Remains to be seen. Point is she’s just a child (and I like playing devil’s advocate).

Lies, they never fix a plot hole next season, they just ignore it
 
Or worse, pretend it wasn’t actually a plot hole and bring it up on every occassion

@PaintEdits  
Or she was just born pure evil.

Yeah this is not exactly a plot hole except this comic that is actually a plot hole  
and naive,ignorant,oblivious to the whole 25 & 26 episodes not to mention its pretty blunt that  
Ponies can only accept an or tolerate so much to a certain level and have high or very high standards  
in what they deemed is ok or not ok to do like when Rainbow Dash did to the weather factory when it came  
to tank in that one episode an that one time that Rainbow Dash was pranking everypony and pranked her back  
in 28 pranks later an when Discord betrayed everyone especially FlutterShy and Trixie for the Alicorn Amulet  
an when Twilight Sparkle used that Magic Spell on her doll and everybody wanted it.but one things for sure  
when it comes to taking over Equestria and or getting rid of magic all together that is where the Ponies  
draw the line.

@noradtwo
 
Exactly

Starlight was only forgiven because she was willing to change her ways and accept forgiveness.