Wow, you might want to talk with some professional help to help her get through this. It is normal for teens to become rebellious. It is a time where they want to spread their wings and get out on their own (which means they are normal) but afraid at the same time because it is a big scary world out there. And the confusion in their own mind is hard to deal with. They call it "tearing". Not knowing the relationship she had with her step-mom before this makes it hard to determine if this is something new or just on-going.
There is that time when most teens believe their parents have been struck stupid and have no idea what they are going through. Luckily my daughters got through it fairly quickly, but there were times wanted to just lock them in their rooms.
Sometimes it does take some time away from our parents to know what they truly do for us. We have taken in several teens over the years to help them see the light. It usually took about 3-6 months, but they ended up moving back home with a much better relationship.