My Wild Horse King by Bridget E. Baker

From birth, Katerina had everything. Born into a wealthy family, she received an impeccable education, and luck gave her both intelligence and beauty.

Until she screwed it all up by falling for the wrong guy.
Cursed by the same incident as Aleksandr, Grigoriy, and Alexei, when Katerina finally wakes, the world’s practically unrecognizable. She also can’t use her magical powers or shift into her horse form without villainous intervention.
When Katerina discovers the information her powerful and vindictive ex has been searching for, will she use it to destroy him or regain his good opinion? The last time, she bet on the wrong horse, and she doesn’t plan to make the same mistake twice. But how can she be sure of the winner before the race is over?