People have refused that Qi Heng could be with Bai Li because they proposed him to someone else.
He was angry and finally told angry "If I can't have him It's will be the end of me" and walk away with a knife.
When he was alone he was crying, he doesn't wanted to die or do something drastic because he wanted so much to be with Bai Li.
They were mean to be together.
One of his servants saw how he was and decided to send a missive to the team of Bai Li for do something when he have received this, he was with his army and said to the army "We have to attack this palace, we need to kidnap someone"
So with his army, they have attacked the palace just to kidnap Qi Heng.
"I'm here to save you, it's will not be the end of you, we are supposed to be together"
Nobody have heard of them later, story tells that they have lived for a long time together, some other way they have die together at the same time in one battlefield.
Nobody will know because it's was their destiny