The chances of Dean being monogamous is somewhere around 0.0001%. Now, as far as I know Nyusha has not had a study boyfriend, so it could very well be the case that she's just the next Candy and she may be like most women, territorial of her man. Guess time will tell. My best guess right now is that she is the jealous type and she's not going to be happy with Dean fucking anything that will let him.