My thirteen year old stepdaughter has been living with us since June, and I feel like I am failing as a stepparent. She was having a hard time at home with her mother and stepfather, so my husband and I said she could live with us. When my husband is around (he travels a lot for business, usually once a month or more), everything is great. She abides by our rules and is a joy to be around. However, the second he leaves, everything is awful: she breaks curfew, mouths off, uses bad language around my kids, along with other typical, unsavory teen behavior. I feel as though I have really tried to include her in our family, but she just seems unhappy. I just had a baby, so it has been especially hard. I have discussed this with my husband, but he just brushes me off. At this point, I'm really not sure what to do. She has put an enormous stress on our marriage, and part of me wishes she would just go back to living with her mother. I do genuinely love and care about her, but at this point, I'm ready to throw in the towel. How should I fix this? 
