I think what you’re failing to understand here is that the human condition dictates that while in survival mode most (if not all) of our decisions will be made from selfish POVs. This is the case for Doyeon, Jinjoo, Jinjoo’s Hubs, and probably even Doyeon’s sister. Until that survival instinct subsides our brains won’t allow us to process our shitty behavior. I do find it interesting tho, that you’re relating to Jinjoo more and even ignoring the fact that she too manipulated Doyeon while they lived together and also made selfish decisions. It’s only now that Jinjoo’s in a position of power that she chooses to display empathy to her important people. It’s the same with her Hubs that he can finally understand the consequences when he left Jinjoo holding his bag of shitty debt. Their survival instincts seem to have subsided while Doyeon’s is still in full effect.
Constructive reply which is rear when I post a comment,POV is important and I try my best to see them from the characters,yes Jinjoo was abit selfish and a tad minuplative but she had no choice because she was in survival mode and yeah Doyeon learnt it while as a child at the orphanage,there's no excuse for the dirty pedo husband but I big up Jinjoo because I feel like her life has been worse off than Doyeon's has been and I feel like Doyeon was actually given a chance when she was adopted to have a better life but Jinjoo didn't get that,she went from a highscooler to a wife married to a pedo who always was running and moving away from debt collectors,Jinjoo was like a obedient dog is what the loan sharks said about her,she looked a mess while her husband got well ironed suites.
Jinjoo said that Doyeon shinned more than she did at the age of youth,which I feel like Jinjoo had and has alot of growing to do mentally and emotionally and I see that she's actively trying WHILE Doyeon is busy obsessing over her body more than trying to treat her well.
I still hope that the two don't end up a couple but it's not my story to tell cause I'm not the writer so I wanna see Doyeon's development bit as she is now so far I think she's selfish,cruel,possessive and a tad crazy.
Well a good person's intention behind giving a drink wouldn't be expecting a dance. If he wants a dance, he will talk it out.
One thing I forgot to mention is the limit of those expectations which follows your example.
Buying a drink and expecting to start a conversation is OK, expecting a dance is delusional, expecting sex is absurd.

So since Doyeon was a kid she pretended to be a good person so people would like her,so it's why she treated Morae well even though Morae still didn't like her,Doyeon continued her act at school is why the teacher found her abit scarry and I guess that she thought treating Jinjoo well would have made Jinjoo like her or even love her then choose to be with her easily over her husband.
But being a good person doesn't mean anyone owes you love,attention and affection,a good person just does good by others without expecting anything in return,so I feel like Doyeon is more selfish rather than selfless and even abit manipulate,Doyeon has a lot to figure out and deal with before dating anyone.
Jinjoo on the other hand as I said before, she is actively trying to figure out and work her shit out where her marriage is concerned and work out what's best for her own life going forward and that's great.