She was just a normal teenager who did laundry services to augment her family's income when she unknowingly used a detergent stick infused with Substance X. The mysterious ingredient created an unexpected reaction with the water ans her genes, giving her body supernatural strength and durability. The clothes she was washing (hers, by coincidence) was also affected, making them impervious to bullets. It was a good thing that the frocks were a matching set because it became her costume. You have to look good while beating up the bad guys, after all. Her weapon of choice is the steel-hard bareta that can knock any goon silly. Funky as her wardrobe selection is, there won't be any up-skirt peeking while she's busy kicking ass. She remains, after all, a modest Filipina girl. When she is done with the criminals, she leaves them nicely tied up for the police to arrest. She avoids being seen as much as she can, but whenever her captures are found, there remains a fresh, just washed laundry scent as a sign that moments before, BARETA GIRL was there.
