S.T.
back in my day (dinosaurs and all) i either walked or rode my bike the 2 miles to school. i didn't die if i got wet, and nor did my bike. put a dishtowel in her backpack to wipe off the seat. or maybe her bum will get wet. it'll just be wet, not gross.
good for you for letting her travel in this healthy fashion! don't get stuck in the tiny, tiny potential downsides.
khairete
S.