My girlfriend likes another guy!

I think the BOTH of you should date other people. You guys sound young. Test the waters!

If she likes someone else, it's already a beginning of the end. Slowly the relationship will unravel, and it will get ugly. Let her go, and find a girl that is 100% into you. The fact that she made a fool of both you and herself in a public place, is a sign that she isn't ready for a adult relationship.

Love hurts, but you should never have to share your girlfriends affections with another man... unless it's her little brother or puppy. You deserve better than that. You'll find another girl to love, and who loves you back. :)

she expected you to break up with her?! sounds like she wanted you to so she can go with the other guy since you've already found it. I'd break up with her. I mean, if you already attempted to try and make the relationship work and she won't let go of the other guy, then your relationship don't mean anything to her! I went through something like this, but it had to do with an ex. finally they stopped meeting each other and talking to each other because I ask for him not to. its made me very insecure now but I mean the relationship is nothing if she likes him and spends a lot of time with him and not you. don't let her walk all over you and make yourself look like an idiot, I went through that and looking back, I wish I would've walked away. yes, you love her, but wouldn't you rather someone that'll love you and only you and you can be with her without having another guy she hangs around with WHILE you are there too? I'd feel awkward just knowing that they like each other and being around them both but really YOU are the one she's suppose to LOOK like she's dating.

I know this must be very hard for you because you do love her, however, I believe you have to love yourself more than her. If you stay with her, there is no doubt she will cheat on you with him. That will be WAY more hurtful than leaving her now. You seem like such a great boyfriend and you don't deserve that treatment.
Do you think she's going to magically stop liking the other guy? No, she'll always have feelings for him whether she sees him or not, and to be with someone who has feelings for another is pointless. You're not being fair to yourself. The best solution to this is to break up with her because the two of you need time. That way, she'll finally realize that you're the better guy for her and she'll come back to you wanting you more than ever...

If I were in your position, I would walk away from her.
But I know that's not the advice you're looking for so --
Just like what everyone else said, she has to avoid this guy. But it has to be HER decision, not yours. She knows that avoiding him is the only way you and her can work it out. If she acts dumb about it, and insists on hanging out with him still, then obviously she wants to like him, and is not willing to stop, or she can't control herself, meaning, she will eventually cheat on you.
If she decides to avoid him, then that is a good first step on working this out. The next thing you two need to do is talk about your relationship. Ask her why she likes him. And ask if there is something lacking in the relationship. You both have to be very honest with each other, to find what started all this. Once you figure out the problem then the both of you could fix it.
The reason why people find interest in others is because they have/give something that their boyfriend/girlfriend doesnt. Or they both share the same interests in something.
Bottom line is, if the BOTH of you are really willing to work on this, then it will definitely work. It might take a while but it will work.

I think she should see who she loves more and stick to that person rather than flirting with both. She shouldn't stop talking to the other guy because that will upset him and sometimes girls just need a boy who they can talk to but they're not afraid of loosing them. Sometimes girls need a bit of time with someone they don't know as much.

She obviously loves you more so you don't need to worry.

bro, she needs to forget the other guy, you legitimately love her and for her to keep talking to the other guy would be sooooooooooooooooooo messed up

If she love syou then yes, quite simple, break off contact with the offending party. If she doesn't you need to find a more mature girl. I hate to say it but most girls can't commit at a young age. Same as most guys. They are all full of hormones raging and can't control their urges. When she got on the defensive right away that was your first clue/sign. Or when she asked who told you, again a guilty response.
I'd say wait until you're in your mid twenties and find a mature girl nin her early 20's. Again she may not be settled down at that age even.

Girl that shares feelings to another guy.
Hard as it is . . Walk away . . Huge odds that you will get hurt even more if this won't stop.
But that's only what I would do. . . For me one of the most sacred things in relationship would probably be loyalty.

Dump her. She's trouble. I know you don't want too. I know that you won't. But I think you should demonstrate a little self-respect and see how she responds.

I know it sounds weird, but a girl has to know that you will draw a line and that you are man enough to hold her to it. Fact is she's been disrespectful, your tolerance of her disrespect will be perceived as a sign of weakness, and her attraction to you will decrease. Woman who think they can have their cake and eat it too aren't worth the trouble. But her feelings for you may change once you demonstrate that there are limits to the bullshit you will deal with. If she wants your love she should have to earn it. If she wants to keep you she will have to abandon her dis-respectful behavior... and if she doesn't want to keep you then you are smart to let her go. There is no point in being with someone that isn't happy.

Any way you slice it, it sounds like she's getting ready to jump ship anyways, I'd beat her to the punch if I were you.