R.T.
OK, this is really, really mean...but maybe she just doesn't like you! I tolerate family members, especially in-laws, because family is very important to me. But I don't adore every single one of them just because they are family. She probably doesn't hate hanging out with you, but maybe she just thinks you're Ok and has no interest in persuing a close friendship with you. Does she have other girlfriends? See if you can go out with a group of ladies and see how she acts toward them. If she is different with them, then I was right and you have to accept that. If she acts the same toward them as she does with you (or if she doesn't have any girlfriends because she really just isn't interested in close girlie friendships), than that's just the type of person she is and you have to accept that.