Gud, how about, "...a sharp-tongued woman with her own agenda"?

I think I'd tweak the end, too, to make it, "...who relies more on her wits and determination than swords and spells," since there are still some swords and spells involved, right?

Hunted by demons and a savage race called the Fari, humanity barely survives in cities protected by mystical barriers. A mad priest threatens that survival when he reawakens the ancient power of Dead Mountain.

Aimee Fallon, a sheltered creator of magical gadgets, discovers a mysterious artifact — the key to preventing an apocalyptic battle — and joins an expedition to destroy the Dead Mountain's threat. On the journey, she is betrayed by those she trusts and left to to face the Fari, demons and a forbidden lover who suspects her of murdering his kin. Her only hope is a sharp-tongued female assassin with a hidden agenda. To save all she knows, Aimee must sacrifice everything she loves.

THE DEAD MOUNTAIN is a fast-paced 120,000-word fantasy adventure mixed with romance and betrayal and a female hero who relies on her wits and determination more than swords and spells.

Thanks for all the input. I think I'm getting set on this.

since there are still some swords and spells involved, right?

She doesn't do spells and barely uses a sword, but other people do.

My mental tongue keeps tripping on:

a sheltered creator

I don't know why, and it may not need fixing, just thought I'd mention it.

I like it, by the way. This last version is nice and tight.

To save all she knows, Aimee must sacrifice everything she loves.

Is there a different phrasing for this? It's got good sound and rhythm, but it feels like I've seen it in a lot of places.

Thanks. A few more things to weigh, but it sounds like I'm close, just tweaking the phrasing now.

And when you tweak, Ricky Nelson lyric to keep in mind:

"But it's all right now, I learned my lesson well. You see, ya can't please everyone, so ya got to please yourself."

Okay, I'm going to make an attempt at query lettering:

Defenders of the Crown is the story of Leah Archer, who doesn’t wish she was secretly a fairy princess. Really, she doesn’t. Sure, she reads an awful lot of fantasy, and sometimes she think it would be nice to have the sort of adventure she reads about. She’s old enough, though, to know that things like that don’t happen in real life.

But when Leah, her kid sister, and her friends perform an accidental spell that summons an unconscious man in a golden crown to Leah’s suburban living room, she finds that the sort of adventure you read about isn’t much fun at all when it’s happening to you. On the bright side, she’s still not a fairy princess-- but it turns out that her little sister, Leslie, is. Which is totally unfair, if you ask Leah.

Leah and her sister meet selkies and dryads, travel underground with goblins, and see what’s become of a kingdom trapped in a ten-year winter. All the while, Leah has to come to terms with *not* being the magical one. And she’d better do it fast, because she’s got to take on the Winter Court.

I got a really nice e-mail from a reader, that's a pleasant surprise.

I like the way you catch the tone of the story, but I'm not entirely sure what Leah is trying to accomplish.

sort of adventure you read about

This bit is in both the first and second paragraph, one of them should probably be rephrased.

She’s old enough, though, to know that things like that don’t happen in real life.

This could probably be shortened. Also, you might want to mention how old she is. It sounds like she's a kid or at least a teenager so her actual age could be important for indicating the target audience.