boys friends sister

I've been with my boyfriend for over a year and I just can't get along with his sister. Sometimes they're super close, sometimes he hates her. I try being nice and talking to her or texting her and stuff but she just pushes it away then bitches to my boyfriend like IM the problem like?? I just don't know what to do. She used to get jealous over our relationship cause her no one liked her ex but she's with a new guy and STILL gives me a hard time. My boyfriend wants me to get along with her and I really do try for him but we just don't click. What should I do?