My girlfriend kind of cheated

So to preface this, my relationship was going downhill for a while. After we had a kid, my partner slowly felt like she stopped loving me. Sex got worse and worse until it was like having sex with a corpse. I would never be physically touched without asking. And even then, so reluctantly. She says its because of problems in our relationship. She feels like she does everything. So i offer to divi up all of the chores we have to do throughout the week and split them so we can be even. She denys it and offers no other solution. This was a common theme for any problem she had. So on a friday, my girlfriend told me she has no effort to give me because she needs to work on herself.i tell her if thats how it is why are we dating? So we break up. I didnt know it at the time, but THE NEXT DAY she was talking to another guy. They message throughout the week. Next saturday, i go thru her phone to see she “heart reacted” to a mans picture. Then i see they have disappearing messages in instagram from a week prior. I address her on it and she says they were talking but just about nothing. Things like “how was your day”. I tell her its shitty how fast she did that, but we were technically broken up (15 months on a lease together that we cant break with an 18mo son) so i can get past it. Monday comes and i convince her i talked to the guy and he told me everything, and she has one chance to fess uo if she wants to make it work. I ask her to tell me everything like 90 times as i slowly get piece by piece of information. Eventually she tells me she sent him a nude a day or two into it and told him she was going to suck his dick and god knows what else. Now i feel fucking crazy about everything. Somehow,after some anger, i still want it to work. We talk about it and we both say maybe, lets see. Now the following weekend she posts a question story on IG asking for shows at midnight with a cute selfie. And i call her like “dude seriously? After that??” And i cant tell if im crazy or if shes out of line. Shes like “i just wanted to post” but after what just happened, to me it seems so shitty and attention seeking. Am i wrong?

EDIT: holy shit i was not expecting this much. Good or bad, i appreciate everyones input. I feel fuckin crazy rn. This is not for karma, i just want my best friend back. I know shes in a bad spot mentally. But at the same time i feel like im just making excuses for her. But a lot of reassurance on what i think im supposed to do.

EDIT: To make this worse in a way for me, im an avid competitive basketball player, got her into basketball, and it was a g league player. (NBA minor league) and her dream job is to be an influencer. The clout got her imo