Wow, I'm really sorry to hear this is happening. It sucks that she said she was fine with it, but when it came down to it, turned out to be a different experience for her; and for you, expecting acceptance and receiving devastation instead. I don't have an open relationship, but I have told my husband that if he did end up sleeping with someone else, I would not necessarily be upset in principle (mainly because I question the logic of monogamy), but that I would never want to know. I just feel like the mental images would get me too upset, even though fundamentally I wouldn't have a problem with it. I think it's a possessive thing. It's weird.

Do you think maybe some kind of counseling together would help? It sounds like she's feeling insecure based on the comments she said to you about "not feeling good enough" or being "afraid you'd leave for a man," and etc. Usually insecurities like that go deeper than just the surface, so maybe there are other things on her mind that's contributing to her reaction to this? Maybe this event just brought everything up to the surface and that's what's making it especially difficult?

On the same note, I hope you try not to feel so horrible, because just objectively, she did agree to the open relationship to begin with, and you acted on what you believed to be a reasonable and mature agreement with your partner. What were you to expect? You were just going off her word. Maybe there's a dialogue there that could happen around the actual open relationship concept? Maybe her feelings have changed over time and she didn't communicate them? Maybe she didn't want it to begin with but was afraid not to go with it? Just throwing things out there, since obviously only you know all the details.

I wonder if this is gender-related? Like, if you had slept with another woman, would she be having the same reaction? One of my exes was bi, and honestly, I always felt sexually inadequate compared to a man, since obviously there are physical differences that can only be approximated. When I found out he was cheating on me with a guy, I was outraged, but I was also really hurt, feeling like I wasn't good enough. I eventually realized that those feelings of inadequacy ran so much deeper than just about the failed relationship... it was nearly every aspect of my life that was haunted by this feeling of inferiority. It was just the cheating incident that brought them all up in my face and forced me to deal with it.

I can just imagine a whole lot of reassurance is what's needed now, even if it feels like it's not getting through at first. She sounds very insecure about it, and probably needs to hear, feel, and see your commitment to her. Extra things around the house, going out of your way to get her favorite things, just finding ways to make things easier for her. I know that will be challenging since you mentioned you're depressed right now too, that doesn't make anything easier.

I really wish you two the best of luck! Keep reaching out here whenever you need.