Altered - The Made Ones Saga, #1

The Eleutians are dying out, one female at a time. To save their species, the powerful Alchemic Clan conscripts women from parallel worlds, altering them into the perfect breeding stock. Kitlyn, a retired circus equestrian broken in both body and spirit, awakens on a strange world in her own much-younger body. She has been transformed into a Made One, but the gift of youth and the promise of a new life come at a terrible price. Rafe, the Wolf Clan's warrior champion, vows to find the cause of the species' decline.
He's certain the Alchemics' bid to save the Eleutians is but a thin veneer masking a dark purpose. That vow becomes hard to keep with the threat of an inter-clan conflict and the arrival of the proud Made One named Kitlyn. To save herself and those like her, Kit must carve a dangerous path in this new reality and make a choice that may cost her her freedom, her life, and the life of the Eleutian warrior she's come to love.