On the newer nancy drew game when I play as nancy and she is talking to people there mouths move to slow so when the words are done being said there mouths still move how can I fix this?

I've had this problem even in some of the "middle" games (like #10, 11 etc), but it's been only occasionally so I never made any attempt to solve it. It sounds like whatever it is, it's gotten worse in the later games.

It might help to know what specific games you're referring to. Common issues can sometimes be found doing a search with the specific game name. As it was, I just went to HERInteractive's site and looked up general stuff and found this:

Sound related problems | Her Interactive

The only related thing really is maybe sound running too fast, but I'm not sure that's really the issue. But it doesn't hurt to check it out.