@ronsboy67 That's the problem with many youngsters today, you need to spoon feed them. They don't understand that there was no need to explain XYZ because it was a plot device! It just did, period. It isn't about explaining it scientifically, youngsters complain even if it is fantasy.
The common problem I've observed with complaints about time travel is that viewers subscribe to a specific time travel _theory_. If it doesn't match their "belief" they are either confused or claim "that's not how time travel works! Rated 1! The writer must be banned from writing and go back to elementary!"
For example, there was no grandfather paradox in the story if you apply other time travel _theories_. We don't even need the multiple worlds/timeline theory! We can solve it with a single timeline! - Theory A: Time bubble. This is my favourite, I've thought about this since early 00s and I'm not the only one who came up with this independently. It just shows how this idea is very flexible and solves almost every time travel paradoxes. - Theory B: Time always choose the best option to maintain a single timeline. The original reality where time travel hasn't happened yet was replaced. In the original reality, the FL travelled back in time through other means. Then she unknowingly changed history, one which led the king on writing the book. When he wrote the book, the original thing that brought her back through time transferred to that book. This reality is now gone, rewritten, replaced by the new reality where the book exist.
@youronlyone I wasn't going to reply, but to save you wasting energy I will. I utterly ABHOR that Drama for whitewashing a psychopath and selling it as a romcom. I will not engage any further on it. This was my first and last reply.