Is there a chance that this will air? I kind of wish I didn't know about this. Now I come back to this comment section every once in a while to see if there's any updates.
Here's my theory. I don't think she ever time traveled or went to a parallel world. I think she's the one the Qi lian knows. She volunteered for an experiment in return for the money to give to her grandmother. The experiment probably put her in a chamber, wiped her memory, and made her think she's someone else. Then something happened and she left the experiment but with this new identity so she obviously thinks she went to a parallel world when she didn't. I think the ML and her will find out she's always been the same person and pursue their feelings for each other. I still can't explain why people are disappearing though with this theory.
Last twilight (currently airing)
A tale of thousand stars
Bad Buddy
KinnPorche
Love mechanics