using sex to get an upper hand is not something far fetched though.I don't think it would fit her character at all, especially in the Zone where she'll be fighting for her life against nature and fallout. Now her teacher did tell her not to be afraid to use her sex appeal to win a fight but that would be her tricking someone so she can kill them. Honestly outside of maybe the raider sisters everyone the MC can get as a love interest just seems way too loyal to be with anyone else without him being the one to tell them to. And even the raiders seem to be more discerning about who they have sex with, like they only do it with someone they respect or they control utterly and it seems the MC is the only one who fits that first category, and I can't see them settling for a lesser man now.
Hell, it's used a lot in the real world.
In a survival scenario, sex, like any other thing is a tool in your bag.