Go to the movies with your friend and his girlfriend and the girlfriend bring her friend along so that you don't feel like the 3rd wheel there?
Most Helpful Girl
Its not cheating unless you take things further or have the intention to. Treat the girl like she's one of your boys and strictly on a friend level. Regardless I think you should tell your girlfriend just so if she does find out she doesn't feel as if you were trying to hide anything from her.1