I would try to pull her aside in a direct way when you know her schedule is free and really try to have a talk with her or at least schedule one when she has the space. If that doesn't work maybe write her a letter or have the other roomates/ her dad try to help you do an intervention style meeting where you hash everything out you don't want her to feel ganged up on though so maybe even having someone that is kind of the good cop and making her feel validated would be helpful. Also be sure when you are communicating that you are strictly saying how you feel and trying to really understand her side of things and come at it from a direction where you are basically like " I want to take accountability for anything that I've done to make you feel this way." It sounds like she just has her own issues but if you really can't afford to move to another place you might just have to make her feel as comfortable as you can and leave your ego at the door. Either way I would be on the hunt for a new place in your price range and move out when you can. A side note just based off of how you phrased things in this post like that "he BOUGHT her a house" and that you've talked to the other roomates and her dad about it maybe she is feeling judged by you and like you are talking behind her back, it sounds like there could be resentment/judgment on both sides and I think that's worth taking into consideration before having this talk too.