I say report him. One day these “innocent” online flirtations may become more serious and he could actually do something to a minor. Maybe he already has. There is no way to know how he’d react once reported. But she has her online proof. And assuming these other girls come forward too, there will be a lot of proof against him. He will be arrested as a child predator.
How were you able to connect the fake profile to this man? The police will ask the same thing. I’m actually curious though.