My girlfriend and I decided before we went on separate trips—mine was for a court case in Philadelphia, her's for her mother's birthday party in Chicago—that we would probably be okay with each other sleeping with other people as long as we discussed it beforehand to make sure we are taking each others feelings into account.
We had ground rules clearly laid out. After my two day drive up, she called me and told me that she had a guy eat her out and if it was okay for her to sleep with the guy. First I was in shock and as the day grew longer I just got more upset about it. I got her to admit that she blew the guy and I just felt so cheated because we where already trying to take each others sexual desires into account. All she had to do was call and say this guy wants to go out later or I'm going out later with this guy, how do you feel about that, is it okay we fool around? Instead she just proceed.
I feel cheated and naive. I was always trusting and thought we had great sexual chemistry. (The day I left, we has sex twice.) We live together and moved to a new city together recently too. I've been attacked trying to save her before and been through crazy shit with her. I loved her more than anything in this world before this but now I feel really conflicted. I feel like I've given so much and all she had to do was take my emotions into account.
Should I tell her to move out and move back with her parents in another state? She can't really afford to live on her own. I'm 28 and she's 23.

She Violated The Rules

My response after the jump...

So... you would've given her permission to do exactly what she did if she had called to ask for your permission in advance but she didn't call to ask for your permission in advance so now you're going to break up with her for doing what she did. Which, again, you would've been totally fine with if she had only asked first. Which, again, she didn't. So you're going to dump her. Because.

I think you're making a mistake. You guys already discussed sleeping with other people. Yes, she failed to honor your agreed upon protocols—ask first, suck later—but it's not like she completely violated the terms of your relationship, SVTR. It's not like she sucked/fucked someone else after making a monogamous commitment to you.

You two have great sexual chemistry and until this/she went down you had strong feelings for her—"I loved her more than anything in the world"—and that seems like a lot to toss aside. I guess what I'm saying is this: I wouldn't dump her for this if she were my girlfriend. But she's not my girlfriend, SVTR, she's yours. If you regard this as unforgivable, well, then you should probably go ahead and dump her. And if her failure to abide by this rule is part of a pattern—if she's proven herself to be untrustworthy generally—then dumping her is probably the right decision. An open relationship requires trust, honesty, and a healthy respect for the rules to survive. (So does a closed relationship.) But relationships also require forgiveness, understanding, and perspective in order to survive too.