For ordinary people, they would probably lose their lives if blood was drawn in such a manner. Yun Qingluo was an exception, as her practice in Kung Fu and cultivation managed to save her life. Despite her abilities, the procedure still had to be conducted with special tools as a precautionary measure.
Gu Xijiu finally understood why Di Fuyi had been so protective of Yun Qingluo. He needed to take the blood from her heart to get the cure for Gu Xijiu, so he needed to make sure that she was alive by keeping her out of danger. She finally understood his intention.
She was smart enough to figure out the rest of the story from there though she did not know how to feel about the situation. After a while, she suddenly asked, "Why did both of your souls leave the swamp together?"
"I fell into her trap," Di Fuyi continued to enlighten her with a few details.