For example, she knew from history books that someone would die and she saved him.  Or she knew there would be a dispute and prevented it. Or she watched that historical drama so she knew the plot and future.  The most important thing is that she should know something and change it.  No matter what it will be

  • Moon Lovers: Scarlet Heart Ryeo
  • Mr. Queen - Slight quirk here. The modern day person is a man. His soul travels back in time and enters the body of a noble woman who is about to marry the King, and as a result he basically becomes the FL of the story.
  • Live Up to Your Name - The modern-day FL doesn't recognize him until later (so she's not using knowledge she gained about history in the future in order to influence the way events unfold in the past, she's just using her modern day medical skills), but she and the ML save the life of Japanese general Sayaka, a famous figure in Korean history who defected to fight for Korea and became Kim Chung-seon (pen name Mohadang). The implication is that he would have died / would not have become the person he is known to be today in history, if not for the leads' intervention. 

Blue Birthday 

Back to 1989 (guy travels back in time)

Love Destiny (Thai) (maybe fits)

Mr. Queen +2

 Yuki31:

For example, she knew from history books that someone would die and she saved him.  Or she knew there would be a dispute and prevented it. Or she watched that historical drama so she knew the plot and future.  The most important thing is that she should know something and change it.  No matter what it will be

For me, who watched so many dramas, its hard to sort it but i think that you should look at these list, maybe you will find what you are looking for: https://mydramalist.com/list/1xrP9eb3 https://mydramalist.com/list/10dVkek1 https://mydramalist.com/list/1dOega54 Maybe one day when i will have more time i will look at it and create new list.