She knew a long time ago that Qin Yan would not love her.
This is an established fact and has nothing to do with any other factors.
He was a friend who was entrusted by her father to take care of her during his lifetime. Apart from that, during the thirteen years they got together, there would never be any other relationship or any feelings outside the orbit.
Some people's love is like a warm sun, illuminating the heart; some people's love is like a dagger, dripping with blood.