Ehhh... why do the ages have to be so young, anyway? I realize that this comes up a lot in manga, but somebody getting called "Goddess of War" at 15 or 16 years of age is pushing it a bit, innit? I don't think the story would've had to be changed at all if she was like 14 at the party and then 20 in the original timeline.
about the gap but we'll see how they deal with it