Hope was driving to her mother's gallery when a supervillian called the Teatime Anarchist blew up the bridge. Thus triggering her own "breakthrough." She pushes her way out of her car and starts heaving about concrete to help.
The oldest superhero team shows up -- superheroes, after all, started only ten years ago, during the Event. Hope, indeed, was eight at the time, though young enough that the disruption didn't really fully register. Atlas, the first superhero, takes her off scene and to their Dome, so that her identity does not become public. They test her, finding her superstrong, capable of flight, tough, heals quickly, supersenses -- and recruit her as Astra.
At one point, Atlas explains why he adopted the get-up, mask, and codename, even though he, like most superheroes, broke through in public: things were terrifying enough for people after the Event and the disasters it brought about; to label these people with powers as "superheroes" helped calm things down.
Further adventures ensue. More about the Teatime Anarchist. A character Hope meets in a club and notices is room-temperature and breathes only when she needs to speak. Rescuing a cat from a tree. The growing supervillain subculture and its problems. Disaster relief and a sudden attack. and much more. I really liked one.