Is NOBODY wrong in the post ? POST : I'm on my phone and not native English speaker, sorry for that.

So, a little backround.
My parents are divorced and my sister (19) and me (21) go at my father's 1/2 weekends. 
I'm an university student with two jobs and one theatre activity so my weeks are pretty busy and I only have the weekends to relax and enjoy my hobbies.
My sister wants to learn canine education but since there isn't any school for that she has courses in the afternoon twice a week for a total of 5 hours a week. I'm absolutely not judgemental about that, that is what she loves and I'me sometimes even more supportive than my parents (because she didn't want to go to univesity)


There is the issue.

She has an exam tomorrow and has spend 4-5 hours studying yesterday. She told me this course was easy and felt like it was explained like it was for kids so I don't worry for her at this point.

In my father's appartment we share the same bedroom (where our desk is) that is the quietest place there because it is at the opposite of the room with the television and the computer my dad works on.

So after lunch I say I need to use our room for one hour because I need a quiet place. (Because I needed to record something and I didn't want them to hear that).
She accept even if she is obviously annoyed but I don't pas attention. My dad saw that and said that he could swich the tv off for her to stay there and study but she said no she wanted to be in our room.
So I do my thing in there and 40 mins later she comes in with an angry face saying that she needs to study for her exam, I say that I'm almost done but need some more minutes and she storms out. like five seconds later my dad comes in saying that I must leave her the room because she has an exam. I answer that she's had the whole week to study and that I only have the weekend to do my things so it's not my fault if she runs out of time for this test (that's only at 18:00 tomorrow!!) And my dad then say that MY bad organisation must not impact HER studies.
I couldn't even answer that he also stormed out and gave me five minutes to finish.

I obviously can't do that in five minutes  but I clear the deskop anyway and go find my sister. I tell her the room is free and she says "THANKS" like I owed that to her for decades. 

I now feel like I'm the AH by the way they both talked to me even if I feel this was all unfair.

So AITA for not wanting to let my sister in the bedroom despite her exam ?