The utility of attaching your feet to the pedals, either with clipless, or flats with the long pegs, is so your feet don’t fly off in rock gardens. Having a strong stance is more important, but clipless helps. It also helps doing bunny hops and things.
The kind of pedal and shoe you use is a personal preference.
That said, she wouldn’t have been hurt as bad if she had been riding normal pedals
My friends are mountain bikers.
The utility of attaching your feet to the pedals, either with clipless, or flats with the long pegs, is so your feet don’t fly off in rock gardens. Having a strong stance is more important, but clipless helps. It also helps doing bunny hops and things.
The kind of pedal and shoe you use is a personal preference.
That said, she wouldn’t have been hurt as bad if she had been riding normal pedals