Chen Mengying is a kind girl. To take a step back, if the person Xiaofan initially liked was her, the two would make a great pair.
They could hold hands through college, then find jobs together, get married, and have children. Living a carefree life, detached from worldly concerns.
Of course, if Chen Mengying were to reveal what happened last night, there's a one hundred percent chance that Xiaofan would take responsibility for her. They would still work together after graduation, then marry and have children. However, Xiaofan might end up with regrets forever. He would never be happy for the rest of his life.
It would be too cruel to him, and Chen Mengying isn't selfish enough to want to bind Xiaofan to herself.
"We can talk about it later. In this day and age, losing a bit of membrane is no big deal. Though I might feel a little guilty towards my future husband, if he truly loves me, he shouldn't care, right? When the time comes, I'll make it up doubly to my future husband."