English is not my first language so bear with me...I (20F) live with my mum, younger sister (15) and my grandparents. I am a uni stundent and I work a part-time job. I would consider myself pretty financially independent even though I still live with my family (I pay 1/3 of the bills and own a car which I bought with my own money + ofc everything for myself). No one expects me to work or financially provide for my family, but I sort of feel the need to given that my mum is a single mother and the only member of our family that is able to work and earn money, other than me ofc. I have to admit I hardly find time for myself and I should add that I'm not the cleanest person (my room is always a mess, especially during exam season). Now to the problem. I noticed recently that my sister has fully hit the "puberty phase": she started to openly disrespect everyone, demand more privacy and respect and have more emotional outbursts that are impossible to explain. She is annoyed by everything (especially me) and gets really defensive and agressive whenever I point out this kind of behaviour. I am aware that she is a teenager and that I once behaved exactly like her, however the difference is that I was held to a much higher standard when I was her age, e.g. I had to do household chores, clean up after everyone (not just myself), get good grades, I wasn't allowed to own makeup and expensive products, etc. Even though I used to find these annoying, now I'm really thankful bcs it made me very down to earth and realistic, so I would expect my mum to treat us the same, but that's just not happening. My mum doesn't "punish" her behaviour, actually she doesn't do anything about it and expects me to deal with it. Idk if she has just had enough since she already went through this once with me, or she simply doesn't care. To paint a better picture I'll give you a rundown of a fight we recently had. I was late for work and had to take a quick morning shower (I had to leave at 8 and it was 7:30 at this point). I go to the bathroom and my sister is there doing her skincare routine. I ask her to let me use the bathroom for 15 minutes and when I leave she can countine without me disturbing her. She tells me that it's my fault that I didn't wake up earlier to use it and that I have to wait for her to finish (this was during the holidays so she didn't have school/didn't have to go anywhere). I ask her why and she doesn't give me an answer. I then decided to just use the shower while she is still there since I wouldn't bother her, but she starts punching and pushing me out of the bathroom. I ended up calling my mum to tell her to get out or let me use the bathroom while she is still in there, but my mum told me to stop bothering her and deal with it myself. This has now started to seriously affect me since I have to strategicially think about when to use the bathroom or the kitchen, and I often end up either not showering or not eating bcs my sister is there doing her thing (this is only a problem for me if she doesn't have to go anywhere and I do). It's gotten to a point where I don't do my makeup or wash my face in the morning bcs she (a freshmen in highschool) takes 1h in the bathroom to do her makeup. I understand that she is insecure at her age and wants to look good, but I also think she needs a reality check which our mum "doesn't have time for". She spends huge amounts of money on makeup, skincare and clothes (that we realistically don't have) and is blissfully unaware of how this finacially strains us, she doesn't clean up after herself and I often end up picking up her used pads and throwing them in the trash - and whenever I scold her, she says that I also am a pig and don't have the right to educate her. Since I work, I am very much aware of how big of a problem money has been for us (and I have been since I was a kid), but I think my sister still never takes no for an answer (she often asks me to drive her somewhere which is often a distance she can either walk or take public transport, or buy her something she saw on TikTok). Whenever I buy myself something a bit more expensive, she ends up using it or taking it, so I also have to keep everything in my room (my shampoo, razor, hair mask...) She also takes my clothes without asking me, which wouldn't be an issue if I had other clothes to wear that day, but my closet is pretty small so I end up wearing something too tight or too big to uni/work because she took the clothes I had originally planned to wear (her excuse is that they fit her better/are nicer since my style is really appealing to her). She also never returns them and just decides they are hers now. Also recently, my friends caught her vaping...they ofc told me, but I decided to have a talk with her rather than tell our mum since she already has enough things to deal with. Again when I tried to reason with her, she told me that I am not the one to talk since I started smoking when I was 17 and am still a smoker. I do think she is right here since I didn't set a good example for her, but I still think she is too young and simply thinks it's cool (again I was once just like her). I don't know how to deal with this whole thing without sounding like I'm teaching my mum how to parent or causing my sister to have a tantrum. I also feel the responsibility to act like her parent since we don't have a father, but my mum is very sensitive about this and usually doesn't like it when I try to get involved. However I also think expecting respect and privacy in our family home is the least I can ask for. I am aware that I am beefing with a 15 y.o. but the whole situation seems so ridicilous and frustrating. I should note that up until this point me and my sister have been inseperable so I don't understand what is causing all this. AITA and should I just deal with this until I move out?