I have this mage character who's disabled with limited mobility (I'm planning for her to have severe ataxia, but the exact disability I give her might still change). I have a couple questions/thoughts about how I should portray her. It's a medieval fantasy setting.
She's… not very morally good. She's currently with a group of bandits (AKA: she robs people). She hasn't got some "I want to kill people because the disability makes me miserable" thing going on though, and most of the other bandits are abled, so her being evil/morally grey is not unique to her. Also, if I ever end up actually writing the story, it would be from her perspective. Does this make it ok, or does it fall under the "disabled villain" trope?
Mobility aids? She would definitely need one, probably a wheelchair, since she can't walk unassisted at all. The thing is, her family is a bunch of ableists who kept her in her room all day because they found her disability "shameful", so she doesn't have a mobility aid (except maybe a clunky wheelchair that needs to be pushed around by someone else). And she definitely isn't going to have a mobility aid around when she gets semi-kidnapped by the bandits (as mentioned before, she ends up joining them). When they're actively robbing people, she'd ride a horse, but what about when they're in the bandit hideout? Making a wheelchair seems hard and time-consuming. I could make her magic powers be telekinesis or (short-distance) teleportation, but that might also be erasure and I don't want that. Any suggestions?
For the first half of your ask, that sounds perfectly fine, because disabled people don't have to be morally perfect! Especially if the story is written from her perspective, it's actually pretty important that she's not just a 0 flaws character. It's perfectly fine that she's morally grey, an anti-hero, whatever, as long as she isn't the only one that is these things as a disabled person.
The "disabled villain" trope is more like, the disability is what makes them evil, or they're the only disabled character and they're evil, basically equating disability to moral failure and to villainy. Other bandits being of similar morality to her but abled is a huge deal in terms of sidestepping the disabled villain trope. As long as she's not the 'most evil' in her bandit group and the only or the most disabled one, this works just fine.
For the second half of your ask:
If the bandits let her join after kidnapping her, they presumably want her there. This means that they would probably willing to help her get or do things that she needs to do in order to continue to be there with them, and that can include them helping source a wheelchair or a walker or a rollator. Maybe they make it themselves, maybe they steal one, maybe they kidnap someone who can make it for her, maybe something else. But if they're something like her friends or found family, they'd probably want her to participate in things, and they could help her get what she needs to do so.
As to the powers, they could be erasure. They don't have to be erasure, but they could be. But to be honest you don't necessarily seem attached to those as her powers, so you could choose something else instead.
As to ataxia, since you mention not being fully decided on this yet, make sure you research how ataxia, particularly severe ataxia, would affect her. I don't say this to say she wouldn't be able to ride a horse — paralympic athlete Mari Durward-Akhurst has ataxia and participtes in paralympic — but I mean that you'd want to look at what she needs to do that and how it affects her daily.
As to mobility aids (sorry for saying as to so much), many people with ataxia use wheelchairs or walkers or rollators. Rollators are wheeled walkers, basically. If she'd be able to use one of these in the hideout definitely depends on the hideout's layout and access. But maybe they could have a hideout with ramps, or on a single level or something, as opposed to like... a treehouse hideout. But magic exists in your world, so maybe her aid could have some sort of enchantment. Like, maybe the aid itself can do very limited teleportation and this gets her into the door, for example? That could be a pretty cool and useful enchantment to put on a wheelchair. But mostly, since you have magic, you have more leeway than in real life as to what the limits of mobility aids are within a space. Or even within a space itself; maybe the entrance steps have a button that can turn them into a ramp. Things like that!