Hi! If you have watched the first few episodes and are still confused as to what exactly the prophecy between Shi Ying and Zhu Yan is, take a look at this comment that explains it in further detail: https://mydramalist.com/61427-zhu-yan#comment-13716805 

An example of where someone thinks they're doing good BUT end up doing evil.  Like the people who give $1 to the beggar on the street only to have that beggar use the money to feed/reinforce his smoking and alcohol addictions.  Or how about the person who donates to charity thinking they did the world some good only to have that money get funneled to black market arms dealers and marijuana growers that in turn kills or destroys thousands of lives.  

So FL thought she did some good to pray for ML only to have done EVIL as a result!

BTW, the discussions in that link above is NO fun.  You all saw the teaser/trailer of Longest Promise where ML got killed by FL...  So yeah, it's pointless to discuss who will be whose doom...  Teaser made it clear FL will eventually kill ML but somehow he will survive or reincarnate and cancel out all the bad karma!