From the pov of a bike rider myself, so many car drivers haven't got a clue that you even exist. If you allow for the fact that the poor girl would have been riding a restricted 49cc, moped she would have been dangerously slow on an already dangerous stretch of road.
Yes, the road needs sorting, but personally I think letting kids without full driving licences ride mopeds is a recipe for disaster. Given the way bikers get treated by car drivers anyway, bikers need more road awareness than car drivers, not less.