C.H.
I know this is tough on you and tough on your step-daughter but you are right in saying enough is enough. The main thing is you and your husband MUST be a united front. You both need to sit her down, lay down some ground rules, explain your expectations of her, behavior, chores, etc... and then follow through. She should start earning some of those special things she's demanding. Do NOT let her manipulate the two of you or be disrepectful. I am remarried and my husband and I always try to work as a team in our parenting. We back each other up at all times and the kids know this.
I also strongly suggest that the three of you get counseling. Again, you and your husband MUST stay united! Otherwise your step-daughter will use you against each other. She needs a place to express her anger and get it out so she's not taking it on the rest of the family. She has a right to feel how she feels BUT there are appropriate ways of showing it and ways that are not appropriate. She needs help finding the right ways to express her grief, hurt and anger. If you can't afford it, get it from your church. Pastors are trained to counsel and offer support. Hope this helps and I will pray for you and your family.
God bless,
Chris