Mostly, it's a matter of figuring out how to resume whatever you'd come to consider routine in the old place. Some of that comes with time, some of it comes with finding new places to store (and then later find) things, some of it comes with setting up hobby spaces and things like that... It's primarily a matter of getting past the stage of "oh, I haven't done that here yet, how do I do it?", because it's those moments of getting bogged down trying to solve a problem that was already solved in the old place that prevent a new place from feeling comfortable and normal. If you take some time to plan out those solutions proactively, it can save you that disruption later on and the new place will feel more like home.
In your particular case, though, where you've got so much anxiety that's going to be disrupted by the change of environment, I'd suggest talking to your therapist to help you find coping mechanisms to get you through the transition. For anyone that's struggling with a transition, therapy can help, but I expect that you specifically will have trouble with "just wait a bit and you'll get used to it" such that getting some outside help is probably a good idea.
Also, if you're afraid to go to the kitchen because your mom might be upset by that, that's not a healthy situation at all. Whether that's your own paranoia exaggerating the risk or her being overtly abusive, that's something that needs to be addressed. Maybe setting up some kind of divider in her space will help to give her a bit more privacy.
Damn_Underscore posted...
Can you take her to court? that is obviously illegal and people won't be happy at her for doing that
Hard to say. If he's been living with her because he hasn't been able to get the disability payments he'd need to live independently, her intercepting those payments is a big deal and she probably wouldn't be able to get away with "I housed him and therefore I don't owe him any money." If he'd be a dependent either way, then the disability money she's been getting for him was meant to help support him and the fact that he's lived with her makes it more likely that it's been used for the intended purpose. It's still not a good thing to do because it's messed with his ability to figure out whether or not he could live independently, but she might be above board.