I know I am late to this thread, but I just got caught up. I wouldn't call what happened an apology in any way. Doyeon did not say she was sorry, she did not say she would not do something like that in the future, and she did not really even express remorse.
What I do think is that Doyeon feels like she has all the power in the relationship and is taking advantage of Jinju. She does not even seem to feel especially bad about this, but has realized that it's possible Jinju is going along with this out of obligation or desperation, rather than real interest in her. If this is the case, Jinju could also still be romantically interested in her husband and planning to leave the instant he shows up.
She has tried to use sexual situations because she finds it obvious Jinju is enjoying it and found that reassuring, but has found herself not satisfied with the idea of a purely sexual relationship. Hence we end on the her asking Jinju if Jinju loves her, ie, is interested in her romantically and not just sexually. She therefore is trying to share her true intentions, including her disregard for normative ethics and social rules (ie a "bad person" by society's definition, the type of person she tries very hard to not appear as to most people), because she wants to find out if Jinju is interested in her romantically both in general but also while knowing this.
Probably what is coming is Jinju asserting her autonomy more and basically explaining why Doyeon doesn't actually have all the power in the relationship. Jinju has stayed with her because it is her best option, not because she is forced to, and Jinju has been willing to engage with manipulative acts to retain that access.
Doyeon has actually been extremely attentive to providing Jinju a safe and comfortable living environment and her disregard for normative rules has been a large part of why she has been successful, eg, not sharing information with the police that turned out to be cake, casually investigating for hidden camaras daily, etc and is someone who is actually capable of doing this successfully (since many would fail even if they tried). If Doyeon can be said to be a "bad person," that is precisely what has kept Jinju safe and relatively comfortable.
Probably we are going towards some kind of "We're both terrible people" resolution that doesn't enable a healthy relationship, as we need to retain the drama factor, but allows them to deepen their relationship and interact more as equals. The author I think has been very careful about writing this in a way where they seem to have contributed equally to the dynamic, even though at different points one or the other has seemed more in control, so it's more or less time for Jinju to reassert herself after Doyeon's wild actions that have gone unchallenged for a while.
