C.T.
Those do sound like scary dreams!! Perhaps do an internet search on vivid dreaming or repetitive dreams. No guarantee what kind of wacko stuff that may bring up so sort through discerningly.
If you have faith in God, pray with her. Teach her how to pray and tell God about all the things she is thankful for and all the ways that He is good.
God is more powerful than any dream.
Also, when you talk to her about the dream, reassure her that you have locks on all the doors and that your house is safe. That you and her dad arent going anywhere.
Also, ask her what she would change so that she can "win" the dream. Suggest that she treat it like a video game. It's her dream so she can do whatever she wants. Start making up some silly scenarios and get her laughing - like she captures the witch in a trap made out of her hoola hoop and the little forest animals tickle the witch and she laughs so hard that she turns "good" and runs off forever to play with the fairies. That will start to break the power that fear has over her.