Living w/ Bipolar Future Sister-in-Law

My future sister-in-law is bipolar, and definitely has some BPD traits, but hasn't been diagnosed with that...just the bipolar disorder. She has recently decided she hates me again and that she is good friends with my boyfriend's brother's girlfriend. (at the beginning of their relationship she absolutely couldn't stand her) It wouldn't be a huge deal to me if I didn't have to live with her. She's accusing me of stealing her Vicodin, which I didn't do. I understand her concern, and I'd have trouble trusting me too because I am a recovering drug addict, but I've been working so hard on my recovery that it feels unfair. Not sure what I should do. This is not a good environment for me to live in, but going back to my BPD mom won't help either. What do you do when there is no safe place for you to go and just breathe??? I tell myself to stay optimistic, but on the inside I'm a wreck. My boyfriend is just fed up with both his sister and his mother and wants nothing to do with them, so he's not much help. He just doesn't want to talk about it. I don't blame him. I guess I'm sort of just venting, but I'd like to hear some feedback too. Thanks.

((Hugs)) firstly.. Being accused of something it's absolutely horrible feeling.
I don't know you situation, but is there no way you and your bf could get you own place?

We are trying, but it's going to take some time. We both work minimum wage jobs and have debts we are trying to pay off. He owes his mother money and wants to settle that firstly, and I respect that. It's just hard trying to be positive with someone so negative around. And my mother is just as bad. :/