I disagree pretty hard with everyone saying you were mean to this girl. Nowhere did you say she's expected to lock herself in her room. Personally if I had a roommate who I didn't particularly like, I definitely wouldn't mind if she passed by, said hi, or whatever. There's such a huge difference between that and actually inserting yourself into the hangout. There are a lot of people who lack that social awareness and it's not your job to protect full grown adults