very upset stepmom from La (submitted 8/5/10)

My husband and I have been married for 10years, we have two kids together, about six years ago his daughter from his first marrage came to live with us when her mom had problems and we felt that she could no longer take care of the child.. Things were ok for a while, there were always ups and downs. Now my stepdaughter is 15 and giving us more trouble than ever.  I feel so helpless and yet I feel responsible for everything... She has never been a respectful kid but I grew to over look a lot of what she said because of how she was raised at her moms house.. Now my kids are getting older and are picking up on her bad habbits, when I disapline her(my stepdaughter) I get fussed at by my husband that I don't do the same to the other kids.. My step daughter does not have much to do with her mom she might talk to her once a week and see her once a month.. My husband says that I need to be more like her mom and love her and show all the affection that I show to my kids.. When I have tried being loving and affectionet with her she pulls away. I am so confused and tired of being blamed for everything that goes wrong in the house..Can you give any helpful advise on how to overcome some of the past and how to be close to my stepdaughter put still be the mom in the house and have rules and consequences for all the kids...