I'm still not sure why people are so convinced that the flashback(s) in the opening of ch 15 are about abuse. They might be, but afaics isn't clear at all.
The first two images of her ("joy, "loneliness") could be years apart (hard to be sure hand drawn with very different angles, but skirt length and hair length seem slightly different; we don't get a clear look at her clothes or body in the second one so no age/time cues there).
Face touching can be comforting instead of fondling.
The clothing being dropped in the last one could just as easily be a coat or jacket as a dress (she is only wearing a dress in the first image, but this is clearly a different location, maybe even a different time, all bets are off). The first "joy" image she seems to be in shoes and socks, the last "fear" image, boots.
We know for certain that at some point in her past Ayako has had moments where she was being informed of her parents' death and of her husband's, no reason that couldn't be what this is.
I'm sure Taiyaki could do something interesting with a history of abuse but as a first/only interpretation, piling even more trauma into Ayako's history seems a bit excessive.