Her grandfather was her father's stepfather, so strictly speaking, they were not related by blood. Her grandfather looked like a kind and upright person, but he was actually a pedophile. He secretly touched Yu Xingxing after she fell asleep. At that time, Yu Xingxing was very ignorant and didn't know that it was wrong. She just felt uncomfortable.
It wasn't until many years later that she realized that what her grandfather had done to her back then was a crime. However, at that time, her parents were on bad terms and kept quarreling. She was afraid that after she revealed this, her mother would divorce her father out of anger, so she endured it.
Later on, the apocalypse arrived.
This matter had traumatized Yu Xingxing. She had not even told Huo Yu about it, so how did this woman know?