We see her back to being a mopey mess when she meets Hikari and all she's thinking about is how annoying her mom is (Yuu is barely in her thoughts) but you think she completely turned that off for 3 months? I mean this in all sincerity, do you actually work that way?
Most certainly. In those months (actually from late February to late July, so 5 months):
1. She had someone very dear in her life, something to always look forward to.
2. Her mother didn't bother her at all, she was still with the stepdad. Yami says as much in that extra chapter
Ever since she divorced her second husband last year after some... well, stuff, she's gotten (to put it nicely) overly involved in my life.
The same mom who used to not even bat an eye if I didn't come home for months now won't even let me stay out overnight.
And since now Yami had someone close to her, she was no longer in a situation where she is alone helpless.
3. She didn't even spend much time at home until the plan was set in motion and she had to stay there to calm her mother.
And after the break up she no longer had that someone who made her life brighter and had all of her mother's bitterness focused on her. So yes, of course it can work that way.
The way you're writing here and earlier about other conflicts make me think you blame blow ups on external events - ghosting due to family matters, school climax due to fate, breaking due to a plan. It explains to me why you write as if being conflict averse is good, because that would be preventing the bad thing (conflict). Which the natural outcome of that world view is that the characters aren't responsible for the bad things because it's not their fault it's just how things happen.
Wrong interpretation and oversimplification of my words. There's no general rule, as in "every conflict is caused by circumstances" or "every conflict is caused by a clash of personalities", every situation should be viewed individually.
If we take the school festival thing as an example - yes, this is caused by a series of decisions taken by characters, but it could easily not happen, had the circumstances been slightly different. "Fate" is not to blame, but fate definitely played a role in there.
And if we're talking about how responsibilities work, if you ever read The Magus by J. Fowles, the moral lesson of that book is close to how I view it (or it'd be better to say it influenced the way I view it).
therefore most of these events are at least somewhat the consequences of the character's actions
I agree with that.
So I see being conflict averse as bad b/c that conflict exists as long as these people are interacting. Like could Aya prevent her mom's suicide attempt?
Which is funny, because she definitely could've prevented her mom's suicide attempt if she actually was conflict averse. By just not going through with that plan, leaving her mother alone and letting her live with the stepdad.