He/she told you, or you found out by accident - maybe a GAG t-shirt was left lying around haha. =P
Also, does your significant other know you have an account?
Just curious if you'd have a problem with it, or concerns. If you'd get rid of your own, shrug and tell them you have one too, send a friend request lol, do nothing, etc.
Most Helpful Guy
Hypothetically, if I have a girlfriend, I'll just be fine with it and wouldn't bother me much. Perhaps, I'll take a look at her questions and answers and see if what she talks in real life matches with her views in her advices she gives in here.1