No idea of publication year, I read it in 2003.  Title is something like “As Time Passes” or “Time Lost” but I honestly only know that it has something to do with time in the title.  No idea on character names, one might be Isabella ??  Plot description: has something to do with a girl traveling back in time to different eras, she meets a guy at one point who she falls in love with, but then travels to another time where she is maybe held captive in a royal castle where they think she is their daughter or something to that extent. I honestly don’t remember how she time travels, maybe because of a book she finds, or some kind of power??  I believe the front cover is like a pale yellow with a girl facing away with a braid in her hair.