You are very welcome OP, happy to help. If there is anything further you felt you could want to ask, please feel free to DM. Either way, a lot of us here are pulling for you no matter which of the various outcomes develops for you.

Sorry, OP. I posted this originally in the wrong place.

These events feel confusing and tense OP, so you are OK feeling discomfort.

In the light most favorable to everyone, on her side she used indirect dishonesty with the other guy. One example was being ambiguous to him--she stated she had BF, but she acted available in exchanging IG. She also acted indirectly dishonest to you both in failing to delete him. So again seeing most favorably, she used indirect dishonesty to avoid the discomfort of telling him a full, "no thanks." I see this as emotionally violent because it is steamrolling her false view on another.

She has been directly dishonest to you in the ways everyone has pointed out: the lie, the double-down, and the several acts of gaslighting. I think you are on to something in acknowledging you could have showed up in the ick of aggro demeanor or whatever. Bigger picture, she used dishonesty to avoid stating her feelings of discomfort around you. As above, I see this as the emotional violence of using dishonesty to steamroller over your feelings, to invalidate you, and attempt to silence you.

I think your only way forward if you want to try repairing things, is to see if you both can agree that you each need to work on emotional communication. If you both do agree, then the toolkit for both of you is the book "Nonviolent Communication" by Marshall Rosenberg. Each of you should Amazon a copy, study it, and implement changes under its teaching.

At the very least, you should buy a copy and study it. By the way, she has to buy her own copy. It puts her skin in the game.

If she won't buy the book, or if she buys it but can't be troubled to make time to read it, you will have another thing you will have to evaluate for what it means in relation to your life.

Hope that helps!

But, to avoid "a conversation like this," all she had to do was delete him. Yet, she kept him knowing that "a conversation like this" could ensue.

Doesn't it seem most likely that in reality, whatever value she sees in him is worth her 1) risking "a conversation like this;" 2) being okay with lying to you to your face the first time; and 3) clinging to her lie, again to your face?

I'd say this guy seems pretty valuable to your GF.

Whether you have that much value to her, only you can evaluate that.