Comes the Flame - The Cassandra Series - Book One by Rebecca Ida Hertz

The Wild West, 1835. Danger lies within. Cassie Harris, a teenager with the gift of prophecy, has a terrible vision of the death of her beloved older brother. Made an outcast by her powers and her relationship with a mysterious god, Cassie struggles against her family and the mores of her times to find and stop the killer – and fate itself. But Cassie’s quest will lead her to a truth that threatens to destroy her entire world.