If Anita didn't have a position of power over Cynric, I actually would just shrug if she'd only slept with him once (if it were consensual, like that could happen in these books), or if she only occasionally slept with him and neither of them was emotionally invested. That he's a teenager would squick me, but I wouldn't be sharpening my pitchfork over it. The fact that Cynric is in love with her and dependent on her is what makes me want to kick Anita in the head.