Girlfriend
To see your girlfriend in your dream represents your waking relationship with her and how you feel about her.
To dream that you are pretending to be someone's girlfriend implies that you are not ready to settle down into a committed relationship. You don't want to be tied down.
To dream that you are meeting your girlfriend's parents is a rehearsal for the actual meeting. You may be nervous about meeting them and it's probably been weighing on your mind. If you have already meet your girlfriend's parents and dream of meeting them again, then the dream is a reminder for you to be on your best behavior. You tend to be more on your toes when it comes to someone else's parents.
Dreaming that you are watching your girlfriend have sex with someone else suggests that you are taking a passive role in your sex life. Maybe you feel that you are not satisfying her. The dream is signaling you to communicate your sexual concerns and/or desires. Alternatively, the dream may reflect a personal fantasy you have.