Seventeen years is a long time to be in the family. But still she should give you both the respect of minimalizing herself where your marriage is concerned. How does your husband feel about this? Does he carry on extended conversations with her? How does the family feel about her? Are they encouraging her to call and stay in such close contact? You might end up having to say something to her. She might be trying to hold on to the past and she needs to move on and get a life of her own. Hopefully all will work out for you and she will slow down on all the interference into you marriage.