The darker elements of the series make me think this could go real bad. Tomikawa's starved for even negative attention, if Hiiragi starts letting her demons out I'm afraid Tomikawa would just be a doormat instead of an anchor. Or Hiiragi keeps swallowing her trauma and falling apart from more of these everyday situations while Tomikawa keeps unknowingly triggering her. I don't think either's really in a position to help the other if their protective delusions of relative normalcy break down.
It doesn't have to go bad, of course. They're tough, they've been able to survive their garbage moms up to this point, they may be able to continue to cope one way or another. I just don't see how they get to a good place from where they are now.