Fantasy novel about dragons (and stopping time?)

Hey, all! Had this flashback of a book today and can't remember what it is for the life of me. I'm pretty sure it's about a truce between man and dragon, and the dragons are starting to break the truce, so the men want to go to war. But there's this princess who wants to help, but she's ignored because she's young or a girl or something. And I think she has magic powers, and for some reason I think a lot of weird time-bending stuff happens when she sneaks out to help. And there might be a jerk prince or knight who ends up falling in love with her? It's very vague, I apologize. I read this book ages ago and Google search isn't turning up anything. I hope it rings a bell for somebody out there! Or your Google skills are better than mine, lol.

Thanks for any help you can give!