The New Olympians - Kate O'Hearn

Emily and her companions, including the winged horse, Pegasus, must confront a legion of Olympic enemies in this third book of an action-packed series.
When Emily's father and the goddess Diana return from a visit to Earth, they bring with them disturbing news. There's a horse called Tornado Warning that's winning all the races, with times faster than anyone's ever seen. What could this mean? Emily, Joel, Paelen, Pegasus, and the sphinx Alexis return to Earth to investigate--and discover a CRU plot to clone Olympians and Nirads using DNA retrieved from their previous time in the human realm.
The CRU has already created dozens of Nirad warriors, Dianas, Paelens, Cupids, and Pegasuses. Now they want to create their own Emily clone--even if the original is killed in the process. Can Emily and her friends put a stop to the CRU's plans before Jupiter finds out and carries through on his own threat to destroy the Earth?