He told her he'd be gone for 2 weeks then 2 weeks later she asks when he'll be back he said I don't know.
That, right there, would have been the cut off point for me too.
They had plans as a couple and he gave her up to go run a pub for a guy he didn't know and shit all over the life they had.
Neither of them are ready for a relationship. She may have ghosted him but he shit on her first. She can't be expected to put her life on hold when she already had it all planned out that was unfair of him. They should have broke it off when he left.
The MC is certainly not blameless here, no question. (Though just to be clear--because I'm not quite sure how to read your syntax--you're not saying he'd been there four weeks when he said he didn't know, right?) However, I agree with
SumTingWong0420, and I think there are a couple things to say besides. One, "she already had it all planned out." Not, note,
they already had it all planned out--
she did. That's really not a healthy trajectory they were on.
Two, and right in line with that, note her reaction when the MC starts talking about going to help his uncle: it's all about her. She shows no compassion for anyone but herself, and no empathy whatsoever. It reminds me of the way Harriet Walter played Fanny Dashwood in the opening of Ang Lee's version of
Sense and Sensibility. (It also reminds me of Sylvia Linsky in
Tex Murphy: Overseer, but that probably means nothing to anyone but me.)
The MC was royally stupid to say "I promise"--he put his word down on an unknown situation, which is never wise; and then he let the pressures of that situation dictate his actions, instead of holding his word as something he
had to honor. He had his ass in a crack at that point and no mistake, but he could have tried to honor his commitments in both directions, instead of just one. He has no right to complain about getting dumped. But that said, her behavior is a lot more problematic, not just after the MC's departure to Oaklane, but before.