I'm honestly a bit surprised by the hate for FMC tbh lol
Not to say it isn't valid, she's definitely a scumbag
But I'm reading her actions as like... Fine? She's never had a physical or romantic relationship before (not an excuse), but she's only just gotten into these types of relationships. Specifically, her only personal experience with it with Maron (and even with #1 girl) has been through payment. It has never meant that it's worthless, but she feels like unless payment is done, she can't really engage in the relationship. She's simply clueless and acting in the only way she knows... Or that's my reading at least