I do hope he does end up talking things out with that other girl. Not saying that he should go back, no matter why she did it, she was still a toxic girlfriend and he was within his right to leave if he wanted.
But from an outside perspective, she doesn't seem to mean to hurt him but is more stressed out and is taking her frustrations on him. Which is wrong, but I have a feeling that there was a chance they could have worked this out somehow or maybe they couldn't.
Still I think it would be healthy for the both of them to talk about what went wrong; even if they still remain apart. Especially for the girl since it might help her grow but just leaving like this risks her wallowing her in depression or anger and getting even more toxic to someone in the future. Might also help her realize she may need to step back from whatever other things in her life are making her stressed enough to take it out on her boyfriend.
Again I'm not saying they need to fix things but that it might be good if they discuss things and break thing off much more amicably.
