Something traumatic happened to her sister and she had to watch her father do something unthinkable... she was young, confused and terrified. Being exposed to such a scene can trigger the body to respond (like feeling turned on) without her wanting to. Sexual desire gets linked with disgust, - so much that you can't have one without the other. So she starts to seek both in selling herself, she's basically trying to hurt herself... I can't even imagine what it must feel like to pretend everyday not to know what is going on at home. Her not knowing if she's jealous or disgusted is a result of all these feelings mixed together, not being able to separate them. She's on a selfdestruct mission. Now, that it's out and they talked it seems to have gotten better and there is light at the end of the tunnel
But I don't know what the mangaka is going for this is actually quite pathetic. The whole premise of why she acts like this is because she's been watching HER SISTER be MOLESTED and RAPED by her FATHER. For some reason she is jealous of that and wants to be...defiled. Or and this is a wild guess HELP YOUR SISTER AND STOP TRYNA WHORE AROUND...LIKE DOES THIS EVEN COUNT AS DADDY ISSUES CAUSE THIS BITCH GOT ISSUE ISSUES