Sure, Diana is a brusque woman, need to be in the corporate world. Or is it law? Whatever. Anyway, the MC is so un-self-aware that I'm shocked she still puts up with him. I feel absolutely no pity for how she treats him because he's an oblivious dick at this point.
There were at least three times she misgendered Christine when talking to the MC and he did not correct her. He finally uses a gendered pronoun instead of the gender-ambivalent "Chris" right as she arrives. I can't figure out why he's purposely sabotaging the relationship, because why else would he do that? No one is that stupid. I hope the character development includes some maturing on his part because I wouldn't want to keep playing a game where the MC can't learn from his mistakes. But if the plan is to help him grow then he's got lots of room for it and it could be a fun journey.
I can only assume that Diana has some deep feelings for the MC (for some reason or history that hasn't been revealed) because otherwise I don't see why she'd still be with him and be trying to fix it up. I expected a different reaction at the cafe when Christina appeared, instead it looks like she suppressed the anger upon realization of how the MC knows the place. Does she acknowledge that MC is being clueless again and quietly forgives him but still gives him the cold shoulder that night as punishment? Or maybe she's just shutting down and avoiding conflict until she can get out for good. Can't tell by the end of this update, but whichever it is it is going to catch the idiot MC by surprise.
I think Christina is sweet, and I hope she watches the MC accidentally burn down his relationship and quietly nope out of there and ghost the MC. That'd be her best outcome.