I have a theory, everytime selene gets sad she gets weaker right? As we can see after Ian and jino rejected her she got blue and dizzy even dizzy enough to trip onto sooha. And taima mentioned "good, I don't have to keep her happy anymore" AS WE CAN SEE THE LAST EPISODES sooha said everytime a "vampire" dies there's a glowing green on Selene's wrist so maybe that's her fuel? And keeping her happy makes her battery stay longer?
I don't check notifications, too lazy to😭