You have read two good books, but if her mother and father haven't read them, you are standing alone. There are a several good sources for information on step-parenting. There is a step-parenting association -- http://www.saafamilies.org -- and a book that I especially recommend, I Didn't Grow Up to be a Wicked Stepmother.
For your step-daughter, a group for children of divorce might prove helpful in this difficult time. Check with her school counselor to see if the school offers such a group or if the counselor knows of one being offered in your community by professional counselors.
Again take care of yourself. You have made a good, smart start in understanding this entire process.