I suggest some short term counseling. Take her to a counselor who specializes in children and teen issues. Her school's counselor might have some ideas, too.
Being jealous is a "normal" reaction but it needs to be managed in a way that will help her maintain a sense of self worth. She has been Daddy's girl up til now. Now she feels the competition for Daddy's attention. It's very real that he won't spend as much time or give her as much attention as he did without the girl friend. This is an adjustment for both her and her Dad. It would be ideal if Daddy would attend a counseling session with your daughter.
After reading other posts, I realize I missed an important fact. Daddy has moved in with girl friend. Of course daughter feels displaced. This is not her Daddy's home yet, in her eyes. Does she have her own room or at least her own space for her things there? It's very important that she does have this so that it feels like her home too.
She's not only adapting to Daddy's fiance but also to a new house/apartment. This takes time. It's important for her to have her own physical space.