Roommate troubles

I’m going to university next year and I planned on staying in residence. I tried really hard to convince my friend to stay on red too and she finally said yes. She asked me to be her roommate and I said I’m still deciding if I want a single room or double. She ends up asking another girl to be her roommate and didn’t tell me she made a decision for over a month. During that time she has said horrible things about the girl she plans on rooming with next year. Am I in the wrong to be upset?

Currently she is ignoring me at school and talking about me behind my back.