My boyfriend's sister hates my guts! what should I do?

I'm going out with the boy I love, he's so sweet he is always telling me he loves me, he is so charming, he gives me all of his attention, he spoils me with presents, he sticks up for me, he puts up with me, He's so cute, smart, sporty (and he has a fit bod ;P LOL) But he has a sister a year older than us, and she doesn't belive in love or anything like that, she think it counts as sexual harasment. I don't mind that, but she is always giving me cold looks. Today I was walking to my class with my friend , she was outside my class room and she said "Oh hiya" and smiled a my friend and turned to me and glared at me. I like her, I think she is really nice , i want her too like me what should I do?