What do the lyrics of She Says by Howie Day mean?

Here's the link to the lyrics:

http://www.sing365.com/music/lyric.nsf/She-Says-lyrics-Howie-Day/E1EDD598FC57AB0248256D43002EF933

I love the song, but I'm confused! What's up with the girl? What's the
whole story?

Thank you so much for answering!