But, how do you know if an ending is truly good for the characters unless you've traveled with them through every page?
Personally, I believe “Young Adult” to be an arbitrary title that means the book "Can be enjoyed by anyone/Has a main character who’s not quite an adult/Isn’t really boring.
Seriously, a thirty-something woman shouldn't be daydreaming about a fictional character in a two-hundred-year-old world to the point where it interfered with her very real and much more important life and relationships. Of course she shouldn't.