We have an adult (20) daughter living at home again for the 4th time. She expects me and Dad to do everything for her, cook, clean, buy, taxi service. If she dosen't get her way she becomes very abusive with her language and actions. Her bedroom is a sty, and the smell is horrible, but won't do anything about it. What can we do?

Stop doing everything for her.

Didn't she have chores and family responsibilities when she was growing up?

She told me that I was not her Mother, (I am stepmom).

Did she ever have regular chores, or was she a princess?

You are good enough to cook for her, clean up after her, and drive her around, but not good enough to be her mom?

First you and her father, need to be sure you are on the same game plan,

You and he start demanding what she is to do, And give her notice to move out if she does not.
So if she will not, you evict her.