The Warrior, the Healer, and the Thief
Diana Jean

Mara is a missionary and talented healer trying to start a new life, one well away from the family she's leaving back East. Ari is the daughter of a runaway slave, a professional thief of mysterious ability who's traveled the country carrying a dark past.
All three prefer to walk alone, but if they're going to survive legendary beasts and powerful magic of the unforgiving west, they'll have to learn that sometimes there's strength in numbers.