So annoying

So I’ve been dating my bf for like 2 years and his sister doesn’t talk to me. Like I see her say hi because I’m a guest but she never says anything thing back she would just look at me. When I mean look at me she would look at me n a rude way. His mom n dad n his brothers like me I talk to them everytime I see them but the sister won’t . The only reason it bothers me is because we went to school together n we were friends not like friends friends but we talk every time I saw her you good vibes now like 6 years later she is pretending as if she doesn’t know who I am. What makes it annoying is that my bf won’t like ask her what’s her deal n y she is so rude to me I try to be nice e erythema I see her n I get nothing. Should I just leave it alone?