SOLVED. YA-ish book about a girl warrior. Setting was vaguely Asian-inspired. She's a good fighter, agrees to protect someone (I think a boy? Perhaps he's a prince?) on a journey. Spoiler ahead. [s]

[Abby]

Sorry about the bad details, it's been a minute; I read it in 2010. I think the cover had her in like silhouette or profile, and some swirly symbols that may have been in the story as tattoos or something. I also sort-of remember a train as they journeyed. Maybe they end up at a temple.

[Kris]

Abby, I removed the potential spoiler from the topic header and added a spoiler alert:
"I think they are betrayed, and I think it's by someone who taught her to fight?"

Spoilers are okay in the comments. Just give us a clear warning first, so the spoiler can be avoided.

[Ky]

This sounds somewhat like Moribito: Guardian of the Spirit, which is first in its series, by Nahoko Uehashi. Balsa is a woman and a warrior, and she becomes responsible for safely escorting a prince to a place of safety. Despite Balsa's age (30s, I think), it read more like a YA novel to me.

[Abby]

Kris wrote: "Abby, I removed the potential spoiler from the topic header and added a spoiler alert:
"I think they are betrayed, and I think it's by someone who taught her to fight?"

Spoilers are okay in the co..."

Oh, oops. Fair enough. Thanks!

[Abby]

Ky wrote: "This sounds somewhat like Moribito: Guardian of the Spirit, which is first in its series, by Nahoko Uehashi. Balsa is a woman and a warrior, and she becomes responsi..."

I read the descriptions and they are remarkably similar. It wasn't the one I read in 2010, though. I feel like I might have gotten it fairly soon after it was released.

[Rainbowheart]

Daughter of the Flames?

[Abby]

Snap! I think that's it! the races sound right, and I know religion was a big part of it. Thank you!

[Rainbowheart]

Awesome, glad to help out!