Is AUTHOR wrong in the post ? POST : English isn’t my first language, sorry for the mistakes.

So I’m 15, my sister is 18 she as two daughters and is currently pregnant. Her boyfriend is going to college soon and they can’t afford an apart anymore. My parents offered her to come back live with us, my sister says yes. Yesterday she came to the house, to bring some of their stuff, and ask me when I was going back to my old room. I say that I wasn’t going to and she start arguing with my parents that since she’s older and have kids she should have the bigger room.

The room I have right now (her old room) is the biggest in the house but there is also a bathroom (with bathtub), a pretty big closet and an another room attached to it kinda like a living-room. 

I need this room because I use the « living room » as a dance studio. I also have too much clothes they don’t enter in the smaller bedroom (my old room) closet, and the room doesn’t have that much place to put more thing.

My sister say she  need it because her daughter, only 1 y/o and 6 months old, need to take bath (I don’t mind letting them us the bathtub) and because she want the living room to serve as the kid playroom (there’s already a room for that but ok?). Her only others reason on why she should have that room is because she’s older and that it use to be her room.

Should I give it back when it’s clear I  won’t have enough place in the other room?

AITA for thinking I shouldn’t be punished because of her bad life choices?