I am at a loss here. I hate rude people and your step daughter takes the cake. What makes it worse is that she probably feels very smug and self satisfied for her behavior since in her mind she is "doing the right thing".
I really don't know what to tell you except maybe that it's for your husband to deal with this since he is the only one she communicates with. Maybe he could tell her that slighting you is rude and he will not tolerate her behavior. But then again, she may stop speaking to him. As a parent, I could not stand being cut off from my children.
So, again, I don't have any real advice. I just want you to know I feel badly for you.
Take care,
changeling