I guess I am wondering what her relationship was like with her father 10 years prior. As someone who had to detach from an alcoholic parent a long time ago, I am sensitive to her situation, but I'm not sure I have all the info here.
But I guess...I'm not sure how much it matters. You can't control her behavior or make her choices for her any more than you can for your husband. And you can't control how your husband feels about his daughter. If you are feeling unappreciated for all you have done for him, fair enough! But I'm not sure what your step-daughter has to do with that.
In the end, though, what you're feeling is normal, and you have every right to it! Please feel free to vent away!!!!