It's fairly close between Jae and Y'shtola but they both beat each other out in different ways such that I can't say one way or the other.

Jae grew up a heavy reader and a theatre kid, so she's a freak in the way a lot of fanfic writers are. Like, her capacity for creativity in that area far exceeds what she might willingly be able to actually do in person. Y'shtola is dirtier in a more traditional sense, in that what she will suggest or do exceeds the lengths Jae'si might initially think to actually do, at least at first (S&M play, exhibitionism, etc.) It cannot be understated that these are still very small margins of difference and they are both very much absolute degenerates who do things like marking each other in public or cold/heat play with magic resulting in light burns or bruises. By comparison, Estinien is vanilla as hell by comparison and thinks they're both absolute batshit crazy but still keeps up a respectable amount.