AITA for demanding my guest bedroom?

I (24F) and my sister (30F) inherited a very nice apartment from our parents in SoHo. Their will sort of just said it’s up to us how we split it up. We sort of decided that because it’s in the family trust just to both use it how we saw fit. Two years ago, my sister got a job in Manhattan and moved there with her family (two kids and husband). Now, I am going to grad school in the city and want to live there as well (it’s basically free and which is super helpful with student loans).

My sister moved into the master bedroom and she gave her two kids her old bedroom and the guest room. The master bedroom and the guest room both have their own bathrooms. My old bedroom from when we stayed there with our parents is pretty small but I loved it at the time because it was never our primary residence.

Now, I want to live in the guest room with the restroom as I am now an adult and have my niece move to my old room. My sister is saying it’s unfair to move my 8 year old niece out but I don’t think so because it’s my apartment just as much as it’s her and she already moved to the master ( which even though it’s much nicer I have no issues with).

On a side note, I also requested my father’s old office, which her husband uses while she uses my mom’s. My mom’s has two desks and is objectively the most beautiful room in the whole apartment. As a student probably going to have to work a couple separate jobs to pay for my education, it would be really nice to have a desk to do HW on. My brother in law is also a stay at home dad and mainly uses the office for gaming.

AITA for wanting to use our apartment like this?

Edit: thank you all for the help. just to answer some of your questions there was no real agreement on how to split it up because my parents died pretty suddenly and the will hadn’t been edited in a while. as for property taxes and stuff my parents trust covers it ( my sister mainly handles that stuff). some people asked about the loans and stuff but basically when i turn 25 in 11 months i get access to some of the cash assets and should be able to pay off everything so it’s not that big a deal. I also wouldn’t want to sell the apartment if possible because my mother spent so much time on it and i miss her a lot and you can see her touch in all the furniture and stuff.