Am I the asshole?

So I've never had my own room until my sister graduated college and went somewhere else, so i ended up getting her room, which i was very excited for. I repainted the walls and tried to make the area feel like mine, but my sister hated that, she said that she wanted her room to stay as hers and that i shouldnt sleep or change anything. I didn't listen though, i mean at that time I was already graduating highschool, and i thought i need a space for me, away from my controlling mom. When my sister would visit home she would sleep in my room (that was originally hers) which i was a bit angry about but i understand that she might've felt homesick, so i let that slide for 3 visits that she did and slept in the same room as my mom like i did before. But however this time i dont care, she has to get used to the fact that its now my space and my privacy. And so after a bit of an argument I finally got to sleep in my own room when she visited the 4th time. My sister would however hang out in my room the whole day, nap in my room, and create a whole mess and saying its not hers to clean up since its not her room, but then she'd refer to everything as hers like "thats my fan" "my bed" "my air conditioning". She would also criticise everything in my room, like how the walls are bland and how it looked better when it was hers, and also stay in my room till very late at night not wanting to leave, and when i would press about it she would say "if you keep telling me to leave i wont leave, dont tell me and I'll leave in a bit" which i did and it was already 30 minutes in and i was getting sleepy, i reminded her that its time for her to leave and she got angry however and slapped my head, turned on the lights and left the door open as she left. Honestly i wouldnt mind if she slept in my room if she respected it, but she kept messing everything, criticising everything and kept referring to everything in the room and the room itself as hers. I never really had a good relationship with her to begin with as she would always put her anger on me, be it physically or verbally and would think everything evolves around her. So what should i do? Should i just sleep in my mom's room again till she leaves which is in 3 weeks or should i stand my ground??