This is after the Chinese Drama, Bubu Jingxin (Scarlet Heart, or Startling by Each Step) about a 21st century lady, who gets into an accident. She get's thrown back into time, and lives as a lady in the Forbidden City of the Qing dynasty. After going through many hardships, the lady eventually dies and gets sent back into the 21st century. She thinks all of this as a dream, but realizes that love can transcend many years and generations after seeing her fated lover equivalent in the 21st century.
This is a fanmade continuation of the Bubu Jingxin, which is called Bubu JinQin (Romancing by Each Step - I think).