How does your family feel about her? Could be a reaction, don't know. I know my husband and I get treated as a "pair" by his family/siblings; I'm deemed really smart (I get books as gifts) because they respect him and think he's smart but they're a little stand offish too as neither of us is very social and he's the oldest brother. His brothers actually talk to his sons more than to us.

Look at all aspects of your family; how your family feels about you, how they treat you, whether she'd feel left out because you all are "close" and kind of exclude her at all (she wasn't raised with you so doesn't have the background/family history; they may resent her for getting in between that) and make sure you don't just want to keep things the "same" with your family now that you're part of a different one; if she doesn't like them and/or they don't like her, which "side" you take will be telling; if there's an actual problem where she isn't treated well by your family, you have to stand up for her and be on her side now, not your old families! You have chosen her and have to keep choosing her to have your marriage work. You can't have both, especially if she doesn't "fit" because they don't like her or because she has a legitimate complaint that you are too tied to them still.