Both mephis and neo had some good points, but honestly, if you want my opinion, here's what I think. The fact that these guys are acting like total AFC nobody's when speaking to your woman probably means that they're NOT going to get anywhere near your lady sexually. Everybody wants to feel wanted and at some level lusted for. If this REALLY bothers you man, you might have to step things up with her a bit. Do some reflecting on your relationship to see where you're both at. Take a look at your interactions from and out of body stand point. As if you're a stranger casually observing. If a bunch of dudes were hitting on my girl and she openly let me know like yours did, I would laugh and bust on her for it. "So which guy are you gonna date when I break up with you? Wine aficionado, or Girafirig?" (Giraffe Pokémon, don't ask)
Just have fun with it man. If things aren't going as well as you might've thought in your relationship, her telling you about these losers could be a shit test. Don't let her know that it bothers you, and I just have say more thing. It shouldn't bother you. Unless he's trying to physically advance or propositioning her, let it go.
You should have other options as well if ya don't. Good luck.

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"Take your last chance. It's not the end..."

I don't understand the guys telling "Just be cool with it and have fun laughing at the AFC guys hitting on your girlfriend". And guys telling that the other 20 guys are total AFC-s and you are not. How do you know that they are ? People in this forum tends to think that who doesn't know about PUA is a looser, have no game etc.

Regarding your gf. It's fine when people are hitting on her, she's attractive. But why does she she have to tell you all this honestly. Why does she have to make you feel insecure in a relationship? Is she that stupid that she thinks that it won't bother you ?

I tend to say to the girls I'm with that it's fine that you talk to guys etc. I'm just not interested so don't tell me, tell your girl friends. If she starts bragging about it, then she goes. And trust me not all girls like that. A normal girl tells a guy that tries to hit on her "I have a boyfriend etc" when it becomes clear that the guy wants something.

Clearly this is bothering you so if it's a good relationship you can tell your girl that your happy that she has fun, just try to keep it to herself.