IMHO, the car driver, though "maybe" unaware of the collision, has collided with your friends scooter, and subsequently left the scene - and witnessed as doing such by her two independant witnesses, which if they are willing to substantiate her claim, which should be reported to the police, as raising a claim with insurers will require a Police reference number. This is to remove any question of a fraudulant claim from your friend, however this will come at a cost in her insurance renewal next time around, although the other driver involved "may" not be insured - hence leaving the scene asp.