Girlfriend has a crush on another guy...?

I understand your feelings. I suppose it's natural to enjoy the attention of someone other than your partner, but the fact that she is initiating these is a red flag to me. I suggest you talk to her and ask her what her intentions are: does she want to stay with you or see how it works out with this other guy or what? Because it's not fair to you if she's considering dumping you; that makes what she's doing very close to cheating.