i do not agree with your 2nd point. she isn't curious about Seju as such because she already knows of Seju's past from the file Seju's brother gave her. I believe in the file there's everything there is to know about Seju's life.
As Seju stated she's attracted to Won sexually, lets not confuse that with love dear.
Though i' rooting for them to be emotionally attached.
True that there's many things about Sumin and Seju in the file the brother gave her but there must be a lot of other things that Won hasn't known yet, Seju's feelings after her seperation with Sumin for example and just as Seju said, many things like that. I know it is possible that Won isn't that curious out of respect for Seju but even when Seju granted her chances to know about her more through this game, Won still didn't catch it but instead, it was only Seju who asked her for more information.
Regarding sexual attraction, I thought we all know Seju very well based on everything that happened in the entire story and the way she reacted to people around her. It's not love yet but it's something more than her usual emotions for anyone else, in fact Won is the second person who could make her act this way. She didn't even open up to Sumin, talk about her things and emotions towards a specific story this much, like Sumin said, they only shared about their dreams almost everyday, she could only know about the suicidal incident of Seju's mom, her family issues through Seju's brother, not Seju herself. Sumin knows they treat her bad, but never knows "How" badly she was treated. If Seju's only attracted to Won sexually, I believe she wouldn't give af about Won's past, wouldn't be curious about the reason why she ran way nor give a second thought on why she doesn't want to ask more when Seju mentioned the joke, or the fact that she also stopped drinking. It's not that hard to see if Seju has feelings for one person, she won't sit in the same table with them, go out with them for some fresh air and talk about casual things of her life or wonder about the other if she doesn't. Just straight back to the hotel or book a room if it's merely sexual attraction.
I get your point very well. Seju has allowed Won to invade her space or rather she wants her to do so, more so to the extent that she's willing to share her story with her even though Won didn't ask about it.
So Seju is being way honest and sincere towards Won but somehow I think she was a bit down when realizing Won didn't treat her the same (Not being curious about her or willing to tell Seju more of her story). It's obvious that Seju starts to fall for Won already, if not she wouldn't think of sleeping with her, but does anybody here think Won also likes Seju romantically? Because to me it's too ambiguous when it comes to Won's feelings:
1. Her poker face
2. Okay, she's curious about Seju but isn't as curious as Seju towards her. In short I feel like she doesn't like Seju as much as Seju likes her.
3. Some parts of her past or secrets that she didn't want to tell anyone including Seju even when she asked her for more. As if she didn't see Seju as somebody close to her even though Seju took her time to speak out almost everything about Sumin - the deepest and most miserable part in her heart, and I'm sure besides the fact that she trusted Won enough to tell that, it was also because Seju wanted to know more about Won's love life and expected the same weight of answer from Won but it seemed Won always kept this arm's length relationship.
4. We don't how much sincere is her kindness for Seju, because the problem is would it the same...would she still care for Seju as much as she does now if she isn't paid that much for this job or just if it's not Seju? Is it her nature that she cares for everybody the same? Is Seju even somebody special to her?