My wife's sister don't like me?

Ok so I have never done anything to my wife's sister but she deleted me off facebook a while back becuase she thought I ignored her when she was over to visit and she got all mad and told my wife to tell me don't talk to her and that I'm rude and all this other crap. Well my wife talked to her and said I didn't ignore her I was actually sleeping when she came over lol anyways she added me back in facebook and now I just noticed she deleted me again......she was just over on Tuesday for a BBQ and was talking to me and everything but I just noticed she deleted me again. I really feel hurt because I never did anything to her for her not to like me.....I told my wife and she is going to ask her why and what's up with her not liking me......... I really don't want my wife's family to not like me.