MyLittleBrother
I just had a thought... Su Yang might not be able to take her yin essence at this time... as she is a virgin, she is still intact down there and as such he will have to pierce her. her blood can literally melt the floor as shown earlier and though he has an extremely strong physique, he would be essentially dipping his wick into a pool of acid poison. he would be immune to it after perhaps but there would still be that initial bit.