In 1520, Magali was in the remains of the Aztec empire before being approached by conquistadors led by an old man in a tattered cloak. While she warned the old man that she would kill him if he got too close, he appealed to her by telling him his story -- that while looking for the Fountain of Youth, he was surprised to find that this myth was actually in reference to Magali herself, a woman revered as a god that he knew could make people young again. While the conquistadors readied to attack, Zoom begged for his youth to be restored and in return, he would protect her. She agreed and within moments Zoom had been restored to a proper age and slaughtered the group. Introducing himself proper, he revealed the source of his and her powers to be the same, the speed force.
He granted her a mission, to help him seek out others chosen by the lightning that struck them, and together "protect" the world from an evil the world would one day know as the Flash (Barry Allen). Magali swore alliegiance to him and she would keep the two of them eternally young as they sought out Human Block, Folded Man, and Top as Zoom's acolytes.
As they trained centuries to face off against the Flash one day, Magali would use her powers to keep the group forever young and in their prime. Their ultimate goal training together, would be to capture and hold the Flash long enough for Magali to make contact, and age him to death.
Imbued with powers by the Speed Force Magali can accelerate or reverse one's aging. She was revered as a god in her time for keeping herself forever youthful and created the myth of the "Fountain of Youth" that had been sought out for centuries. She can age/de-age a person or animal any predetermined amount, as she aged a young bird into maturity, and reverted the then old, and fragile Zoom to an age where he could protect her. She doesn't need to make contact with a person to age them, but rather must be able to see them when manipulating them.