Because when she came back she is in another body and has another name. It's kinda weird if the face are the same.
But at the end of Season 1 , Xian Yuan came back to her modern time and shown no signs of her death in the ancient era. The wrong the production team made was that point. If they want the continuation they have to change the ending of Season 1. And another wrong they made is the First Season is just a TV drama that the new girl is watching. No connection between the First Season and later seasons.
the first season is so pleasing....and the FL is so graceful and pretty. Why did they change FL? If they have to , so all the other cast should be changed also their character names.