Daughters of a Dead Empire by Carolyn Tara O'Neil

An alternate history set during the Russian Revolution.

Russia, 1918: With the execution of Tsar Nicholas, the empire crumbles and Russia is on the edge of civil war—the poor are devouring the rich. Anna, a bourgeois girl, narrowly escaped the massacre of her entire family in Yekaterinburg. Desperate to get away from the Bolsheviks, she offers a peasant girl a diamond to take her as far south as possible—not realizing that the girl is a communist herself. With her brother in desperate need of a doctor, Evgenia accepts Anna's offer and suddenly finds herself on the wrong side of the war.

Anna is being hunted by the Bolsheviks, and now—regardless of her loyalties—Evgenia is too.