Jealousy issues or not?

Hello everyone I'm new here.
I just have a few questions that I need answered.
Today my girlfriend of 2 years went out with a guy, her co-worker, and his roommate; they all went to the mall to do some shopping as she told me. I have never met these guys, she recently slowly started telling me that her co-worker is a nice guy and stuff, they exchanged phone numbers.
It feels weird for me because she never goes out with guys like that. I don't know what to think. It made me upset, how she eagerly just went out with these guys and ditched a chorus concert that she had, which I was going to attend. I don't know what to think. Is it wrong for me to get upset? Or is it wrong that she went out with these guys without me knowing them? She says that I have jealousy issues and I don't know if I do or do not. I trust her, it's just that I don't know those people. Is it okay for her to go out with people she barely knows or people that I don't even know?
Sorry for the long text, thanks in advance.

hahaha a classic move of girls when they want to get with another guy

you're getting walk all over. tell her its bothering you and if she said your just jealous then dump her now before you get dumped.

Yeah it sounds like she has a thing for her co worker. You should ask her whether she has feelings for him, if you know her well enough you'll be able to tell from her reaction whether she does, irrespective of what she actually says.

Uhh, I don't know. I don't want to believe this. All today she constantly been sending text msgs saying "I love you so much","Your the only one for me", "Do you love me?" I dont even think she is home yet. Its been 4 hours already. She keeps telling me that hes not like that. And she keeps asking me if I'm mad? I will ask her if she has feelings for her co-worker when she gets home. But is it okay to get angry at the fact that she went out with these guys? Uhh it bothers me so much.

Look dude, your girl knows you will get pissed if she went out with another guy and she still does it. Come on man! Dont act like you cant see through games.

Lets put it this way, if she really loves you then why would she go out with that guy even though she knows that it will bother you? Does it make any sense?

Go to walmart and buy yourself some balls then put your foot down and tell her whats up. If not then good luck getting dumped or cheated.

Because she says that I don't trust her. She keeps saying that I dont trust her and I have a jealousy problem

Yeah, she's acting suspiciously. You can tell because she's doing things uncharacteristic of her - going out with guys, which you said she never does. Anytime someone does something that is unlike them, there has to be a pretty good reason for that.

Second, she ditched her OWN choir concert? That sounds pretty irresponsible - more like teenager in love type behavior. For sure, she sounds like she's not in control of herself.

Third, she knows what she's doing is wrong, hence why she is overcompensating and sending you text messages telling you how much she loves you. That way when you get mad, she can point out the fact that the whole time she was with them she was contacting you and focusing on you.

Fourth, she's turning her suspicious behavior around and blaming YOU. By blaming you, she's putting you on the defensive and making you feel like you have to suddenly account for yourself and explain yourself. Mission accomplished - you are now completely distracted from the situation at hand, and she gets off scott-free.

Fifth, Now, you'll also start feeling like you have to 'prove' it to her that you aren't jealous, which means there's a chance you might just let her keep going out with this guy (or guys) without saying anything just so she'll 'believe' that you aren't jealous.

Don't let her derail you or distract you from what is really going on. Ask her point blank if she's interested in this guy, and like others have said, you should be able to tell if she does or not (even though she'll likely lie about it). Also rationally and calmly point out her odd behavior and ask her what all that means (while you know already, of course). She'll probably get over defensive, blush, stutter around, stumble around her words, accuse you of being jealous, whatever - anything to get out of the corner you put her in. You should also ask to meet these guys - I'm wondering if they even know she has a boyfriend. Finally, you need to decide what you will and will not put up with. If she wants to continue doing things that aren't appropriate, then maybe you should dump her before she has the chance to dump you (or cheat on you).

Oh, and somewhere in all that,you might also sit down with her and try to figure out if there's something that she is dissatisfied with in the relationship, because perhaps that's why she's being distracted elsewhere. Or, she just may have other issues.

I agree with most of the posts here (because some of her behaviour seems a little weird), but I need to add my further two cents:

It's healthy and normal to have friends of the opposite sex. I have male friends I hang out with, without my fiance. He doesn't mention it, and if he told me he didn't like me hanging out with them I'd address his concerns, but I wouldn't allow him to tell me who I could be friends with. That's controlling behaviour.