If she using the word too often. But don't demand it. If you demand she stop using the word then you are teaching her that censorship from authority is okay. Also you establish yourself in her eyes as someone she can't talk to honestly. Many adults abuse their authority in that way. It's just a word, no one is being harmed by it, so there is no reason to force her to stop. Only time I would step in and use my authority to force her to stop doing something is if she is putting herself or someone else in harm's way.