In the comic books, Allegra is actually the daughter of the villain Wavelength. She was abandoned in Brazil and left in the slums living with adopted parents.

As Allegra grew older and her powers developed more, she was eventually sent to Arkham, but Deathstroke and his Titans were sent to save her. After she was rescued, she returned to Brazil to kill her biological father, and Slade punished her with a power-dampening collar.

Already in the show, Allegra has a much more thorough storyline than in the comics. And considering this season is focusing more on side characters, we're sure she'll be getting more screen time in coming episodes.