Few people who grew up after the early 90s will remember just how sexist that period of time really was. It was before powerful women like Dana Scully, Buffy Summers, Daria Morgendorffer, and yes, the Powerpuff Girls, proved that ladies could kick ass and hold their own even better than the boys. Before they paved the way for more strong female characters.
Amy Jo Johnson, playing Kimberly Hart, was one of those female characters who didn't need to be saved by men. But at the time, it was still a controversial move to have a girl beating up monsters all on her own, and Amy struggled with the reaction. She pushed through, though, and everyone grew to love her and recognize that this was totally cool. And at the same time, the show made her a star.