If you don’t have one in real life, the dream represents a desire for more affection and appreciation. This dream may equally spring from anxiety or from sexual excitement. Often, the girl is actually a reflection of yourself, so take note of how you treat her, because that represents your own self-image. Most girlfriend dreams involve travel - if yours doesn’t, you may be overdue for a trip.
If you dream of fooling around with somebody else’s girlfriend, you are suppressing passion in your waking life. [1]