the human will can be stronger as expected in many cases even if the desire is there to do something that a person not want. if a human think about what is important to him and he has the will to controll the desire that is filled his body they can have powers that he never thought. maybe monstergirls can have a strong will and mind too to controll their lust and will not hurt people in that way they like. only when they have sex with someone the controll is lost and they cannot hold back until she has enough. but how hard the sex is they not wanted that someone will die in that way and stop when a human reach his limit. to lose the person they love is the hardest blow to them.