I’m not a very “b’shitta” type of person, so although I don’t have a TV, certainly don’t go to movie theaters, and don’t generally watch movies, I wouldn’t say “I don’t watch movies” because if I happened to be somewhere and others were watching a movie I would possibly sit down and watch if it seemed interesting.
However I truly don’t believe there exists any non-kids movies today which are “a perfectly kosher movie” — maybe “mostly kosher” or “pretty ok” . .. .I remember when I was in high school there was a certain movie that had come out that was very popular among the girls in my OOT Bais Yaakov. Many girls who didn’t “watch movies” were watching it “just to see some of the great choreography”, and anyway, it was “perfectly clean”. A friend of mine was convinced by someone to join her in watching. About 15 seconds into the movie came the first bit of nivul peh. When my friend raised her eyes, the other girl said “oh, everyone talks like that in the world — it doesn’t count!” — and of course the romantic subplot with the related scenes didn’t count either. . .
Although for a woman or girl watching movies is probably not halachicly assur (men are obviously a different issue), you are definitely introducing many things into your mind that you are better off without — language, twisted values, violence, unrealistic relationships, etc.