Rarity is more patriotic than even Applejack.
So patriotic that when she was a teen when saw somepony use the Equestrian Flag for a beach towel, she yelled at them about breaking flag protocol and allowing your “filthy sweat molecules corrupt our glorious banner”.
After all ever since she was a filly she was in charge of sewing flags. Any other foal who messed up one detail would suffer the wrath of Rarity’s tantrums.
Rarity isn’t “Questria F Yeah” type. She would think that phrase would be disgraceful because it would make Equestria look like a joke.