In the Crystal War timeline, Starlight Glimmer’s obsession with equality manifested differently, with her goal being to achieve equality by improving ponies, rather than by bringing them all down to the same level like her main-timeline counterpart. To that end, she begun performing forbidden alchemic experiments as part of her Pony Upgrade Experiment, using all forms of magic, medicine, and machinery in an attempt to create a super-warhorse serum that could bring anypony to whom it’s administered to the pinnacle of equine potential. However, this was just a stepping stone towards her true goal, to find a way to make ascension into an alicorn possible for all, and create a world where every mare will be a Princess. Rather than an equal sign, she used an infinity symbol to represent the unlimited potential of all ponies. She was eventually apprehended by Special Agent Sweetie Drops, and is now behind bars. Though her experiments were horrific, they also proved very informative, and data gleaned from her records has been vital in the war against Sombra; for example, it was only due to Starlight Glimmer’s experiments with bionic enhancement that flying ace Rainbow Dash, grievously wounded, could be given a wing of steel and returned to the skies.
In the Chrysalis Resistance timeline, she became one of Equestria’s most notorious traitors. As soon as she saw the changelings, she became enamored with the idea of them; a race of virtually identical individuals who could assume any identity they chose seemed to her as though it could be a perfect society of equals. And so she offered them any aid she could, from teaching them about Equestrian society so they could better pass for ponies to rounding up any survivors and leading them back to the swarm. But after the Lights Went Out On Bridleway, she just… disappeared. Nopony knows where she went; some say she finally understood what she’d done and turned herself to stone so nopony could be hurt by her again, while others say that that the Changeling Queen was so pleased with Starlight’s work that she ordered her subjects to make the mare one of their own.