My mom won’t let me keep my medication in my room, what do I do?

So I recently turned 18 last week, I’m a female and I live in a bit of a toxic household. My mom is bipolar and has borderline personality disorder as well as issues with control. I’m not trying to make excuses for her but I want that to be kept in mind.

I have severe anxiety and depression which I take medication for, I keep my depression medicine in my room because I have a routine and I take it every night- my anxiety medication was kept in my mom and stepdad’s room when I was prescribed it last year because she was worried I’d get addicted to it, which is understandable to worry about. Today I wanted to talk to her about it and keeping it in my room since I just turned 18 and now I’m legally an adult.. when I asked her about it, she immediately shut it down saying “I’m legally responsible for you until you are 21 and maybe if you show more responsibility I will think about it.” Which doesn’t make sense to me because one, I do all the chores when my stepdad is at work- plus she makes me cook for her AND my little sister, and two she is not legally obligated to withhold my medication from me. She always feels the need to dictate things about what I can and can’t do even though I’m an adult now, sure I’m freshly 18 and all but it’s still MY medication and I wouldn’t be taking it if I didn’t need it.

My anxiety medication helps me sleep and it keeps my mind from racing all the time. I know when I do and don’t need it and it’s not up to her to decide when I can have it. I’m not sure if she just wants to keep control over me or if she thinks she has a valid reason to do this but I need advice because it really doesn’t feel right to me for my mom to have control over something this important for me anymore. Can I get some advice please?