OK, I feel like this is ridiculous, and honestly, her reaction is more hurtful than the actual action. My relationship with my now ex girlfriend, has been fairly turbulent for the past say year and a half (together 4) and during big arguments, she has a habit of "ending the relationship" but this only ever lasts at most a few days. She does this often, and from what she's said herself in the past, we both know that it's just anger and we aren't really broken up. Immature of her but that's a different story. I recently found out, that on one of these times, where bare in mind there was not a single day we weren't in contact, all be it arguing, she hooked up with someone else. When I found out, her reaction was to bluntly deny that she'd cheated. We "weren't together" so she doesn't even feel like she did anything wrong. Obviously I've dumped her, and she's saying that isn't fair, because it wasn't cheating so I have no reason to be angry. Am I fucking crazy here or is that the biggest joke of an excuse imaginable? She said she's sorry because it hurt me, but is fully insisting that she didn't actually cheat so it wasn't wrong and I'm being unfair to her. So, as afr as I'm concerned, she absolutely did cheat. This was one, at most 2 days of being "broken up" with constant contact, aita for telling her that she is a cheater, and I want nothing to do with her?

Edit to add: we are not teenagers, we're both in our 30s, so the fake break ups in anger is immature enough, but I felt I should add that as I'm aware this sounds like something that belongs in a teenage relationship, which is bloody ridiculous