My boyfriends sister hates me. How do I deal with this?

My boyfriend and I had a bit of drama that made us split twice. (Workplace rumors and dislike from this sister) We recently decided that despite the rumors and hate from his sister we belong together and want to make something work.

I've tried being friendly with her and I'm only met with disdain. She hates the fact that I come over and sleep over at my boyfriend's request and I'm not sure how far she'll go to keep me away. I just heard her angrily complaing over the fact that I'm sleeping over because his house is closer to work and I had to close tonight and open tomorrow. We aren't even talking, I literally just came in to sleep. I guess he didn't say anything because he didn't feel the need to and she's furious, to the point where she had to leave the house because I guess she's that upset. She's also the kind of girl to overreact and take things way out of context and react volitaly to said things.

Is there any advice you guys can give me? I don't know what to do about this but I really don't want to cause a problem. I really love this man, however, and I'm not willing to back down because she has a weird grudge against me. I just want to get along with her and have her stop hating me for no good reason that either him or me can figure out.

I'm also a bit scared for my car at the moment because I heard her saying she was going to grab her bat after coming back from leaving.

So yeah. Some advice would be great.