There were a few instances in previous chapters that show she's not completely "sane" (or however u want to call it) and, as a result, may snap out of whatever facade she decided to put. For instance, in chapter 9 she thought to herself "which one of us is really bluffing" while was was with Dahye, which made it look like she was to extend faking her passiveness and testing Dahye, or even later on when she admitted that she loved the way Dahye was acting around her when they were having sex, despite that for her being a "victim" wasn't pleasant. And Yeonhwa's current behaviour in shop just looks like she's trying to annoy Dahye, so maybe in next chapters author will throw other hints
Thank goodness there are some implications she's playing a facade. I'm hellbent on seeing her break it especially after the prologue in WAHNW states that Yeonwha was feeling bored during custody.
Yeah and a lot of people are also pointing out that she may be only acting, cause there are moments when Yeonhwa seems a bit suspicious, tho at this point it's hard to tell where author is going with their work
What the hell happened to Yeonwha?? Why is someone who sexually abused her sister, manipulated many people and blackmailed a girl for months suddenly the innocent one? Damn Im just going to sit back and wait for her to snap, there's no way she's actually cured of her sociopathic tendencies now （￣へ￣）