AITAH for telling my teenage sister she is insecure and jealous

My teenage sister is depressed. As the scapegoat child I’ve been positioned to take emotional abuse as she seems so focused on what I’m doing that everyone allows her to talk down on me to make her happy. All my mistakes is noticed none f my achievements. I’ve learned to accept myself and be proud of myself. My cousin is at home and she is taking advantage of the situation laughing with my sister at me, purposely not letting me have my much needed space for the day. Age was supposed to stay fur a month Then told us all she is staying for six months.

She has been in my room as sister is studying but I have adhd, I also have depression no one seems to care about I do need time alone. I can’t take someone being in my space more than a month let alone six. I finally put my foot down sister barges out room despite her having her own space saying I dint ‘run shut’ I got out and ‘party and smoke etcetc’

Why is my life on her mind? I’m my own human not an extension to her. I’m too old to be fighting about mistakes I need to start concentrating on how I can build my life so I don’t end up 30 and broke. How do I deal with a sister always trying to put me down. I argue back, talk down on her too so maybe she gets how it feels no. I video her sfe runs away then comes back say how I hate myself? I ignore her kidding not she will stay with me in the sane room till 3am. It’s literal torture now.

I’m should be in accommodation by end of this year but I work and work is stressful enough now home life too? I don’t know anymore I’m just sad all the time and trying to talk positive but it’s so hard right now