Most Helpful Guy
Well... it'd make me uncomfortable... but its not like she can help it. I guess that depends on how much i trust her. If she ever told me about it happening, I'd ask how she reacted. If i was satisfied with the way she handled the situation, it wouldn't bother me that much.
I mean, for instance: One of my exes, when we were together got asked out by a guy. She told me how she replied, "no thanks. I already have the best man i could ask for". It made me feel really good at the time- not only her reaction- but the fact that she actually told me about it happening.
So if said GF did things like that, then I'd be ok with it :)