AITAH for telling my(F18) step mother off after she told me I should go live with my grandparents full time?

My bio mother passed away when I was 12yrs old and my step mother and her two kids came into the picture when I was 15yrs. She and my dad got married last year and she and her two kids moved into our home.

We live in a three bedroom house. I have my own bedroom and her two kids(both boys) share a room. Just today while my dad was at work, my step mom came into my room and told me how she thinks I should go live with my grandparents in order to give my room up to her oldest boy. This immediately made me mad. I asked her who do she think she is coming into MY room that's been mine since the day I was born to tell me that I should move out and that she should send one of her kids to go live with their father since she's so worried about space. I then told her to gth out of my room before I get really disrespectful. Then later today my dad came into my room to talk to me about the conversation between my step mom and me. Thankfully, he was on my side and said that I am not obligated to leave my own home to please her and that she was wrong for making such suggestions like that.

I always had neutral feelings towards my step mom and her two kids. But today made me lost almost all respect for the woman. This is my home and she will not have the power to put me out.