Im looking for the name of a movie where a little girl moves in with her dad or stepdad because she had killed her mom or something I think and now she starts trying to kill everyone that has a relationship with her dad so she can have her for herself. Also, I remember she kill a person with a hammer by hitting him over the head with it

I am not sure if this is the movie you are thinking of but your description reminded me of it. If this isn't it, it is worth checking out. Good, freaky kind of movie.
Please take a look at this link:
Wicked (1998) (http://www.imdb.com/title/tt0120088/)