Don't worry, everybody knows that two girls kissing is meaningless. They're only brave enough to do it when they've had a drink, and you can't read much into anything anybody's ever done when their inhibitions were lowered.
If she's written a song about it, then your girlfriend has obviously noticed that lesbianism is a turn on for men and is becoming better attuned to your desires. You should thank her for giving you wank fodder.
Next time, ask for pictures.













