I just wanted to post about my sister in law and my husbands relationship. I really dont understad the closeness  of it. We use to live states away and now we moved closer and its been difficult getting to know everyone and feeling people out. I feel left out at times and kindof competitive around his sister for some reason. She often tells me she isnt going anywhere and that he is her best friend and things like that. So that leaves me to think where do I belong in all this. She has a good heart a caregiver type of person. She loves kids but there is an underlying feeling I get around her of mistrust of her testing me or something. Its kindof weird we kindof got into a disagreement and I come back outside and there she is hugged up with my husband. I just want to be able to coexist civilly with her and not feel weird around them. I've talked to my husband about this and he gets pretty defensive if I say anything about her so I'm not really sure what to do. It makes me feel sad at times. He just left to fight the war and I'm sad too but she calls a week later after he's gone crying still. Her facebook is all about her brother, like she doesnt have a life of her own. I wish someone could shed some light on this, or do you think I'm overreacting. I want to be fair. Also I cannot say anything without him telling his sister! Arghhhh.

For the most of it I would say you should just respect that they have a special closeness.. especially in the time he is away, not the time to add to his stress.
But this "I cannot say anything without him telling his sister!" would peeve me no end. That needs to be discussed with him when hes safe at home and settled back in.

You say you have moved it appears to be to a place where he has family and friends around him, but not so much you. Under the easiest of times this is difficult to deal with. I would say the closeness of your husband and his sister is magnifying your sense of isolation and lack of intimate personal connections. You need to put yourself in situations where you can meet people near by with potential friend qualities. Join a hobby group eg.

You say she called you when she was upset and crying ( dont judge her for the drama queen stuff, she sounds young and lonely to me, she could probably use the attention ). that she called you is a good sign, she reached out, seeing you as being close to her brother. You might even take an opportunity to share some time together.
maybe not drop your guard too much, intuitions have their grounds ( just be sure its intuition and not frustrated confusion )  but while your distrusting her, remember that she will also be feeling the vibes and back and forth it goes.

Im just saying the timing is off to take any actions that would likely further ailinate you among his inner circle.. that would be cruel to him, and I dont feel will do you any good right now..
come back when hes home and settled and lets see whats going on then.