Does she come from a really small or dysfunctional family? Or is she just an introvert? My Dh comes from a TINY family (at the time I met him he had one grandparent, a father and mother, two sisters and one brother in law.) I come from a HUGE family (oldest of 12, my father is one of 5, one of my aunts had 7 kids who so far have given her 16 grand kids.) It was a big culture shock for Dh and he was very....reserved and similar to how your future-SIL is described. My family is.....let's just say NOT reserved. ;) They all thought he didn't like him and that he was judging them or something. He just needed to get used to it all and it took time to be comfortable with them. Years, in fact, since he only saw most of them every other Thanksgiving.