Parted Waters by Natasha Ashwe

Parted Waters is a first part of a fantasy novel that revolves around the world of two young girls. They are sisters, twins in fact, and they are princesses, daughters of a great female monarch with an unquenchable thirst for power who seeks to rule and dominate all the kingdoms that challenge her rule. The princesses choose different paths, one follows after love, the other after an ambition similar to her mother's, and the paradox of how identical they are in appearance but different in character ultimately determines both their destinies.