Stepdaughter hurting marriage

Hi, LITTLE. I think this girl might be acting this way becouse she felt neglected by her father. And she may need his attention now, so she does as much as she can to get it. Your husband shouldn't be strict, but show her that he cares, if that is possible.
Maybe you could keep showing her that she is like a daughter to you and make her feel accepted as who she is now. Just treat her as an adult and an equal and tell her that you don't want her to get hurt, and that you care about her. Good luck!