Sunset didn't know a lot at the moment.
She knew she was in some sort of hospital, since her memory seemed like it's only missing the useful information that follows the more basic facts (like where the hospital is located).
When she first woke up she'd assumed she was in some sort of violent accident. Her limbs were covered in thin scars, and her head felt like something had drilled through the side of it, but the more she listened to what the few ponies around her said, the less sure she was about that.
At least she knew her name was Sunset Shimmer, but that was only because she read the clipboard at the foot of the hospital bed, and she knew those were usually reliable (except when they're written by less than reliable ponies).
She would probably have known more than she did at the moment if she'd listened to the doctor talking to the giant white mare sitting beside her bed that reeked of smoke and fire. But she'd started to zone out after he'd begun to talk to about "preventative measures," and how she needed a support network and a bunch of other things that sounded like they would've been better said to a loved one (did she even have any of those?) and not to the stranger sitting beside her that hadn't even looked in her direction since entering the room.
There's no mirror for Sunset to get obsessed with, and by extension run away into. Stuck with her spiraling mental health in a castle that hates her as much as she hates it, the pressure reaches a breaking point and Sunset does some things in the night she regrets but doesn't remember by dawn. All she knows is her name is Sunset Shimmer, she's in a hospital, and she doesn't know the giant white mare that smells like smoke.
