I've Googled all manner of things and all I can find is how to make drinking water safe if your camping or hiking. However, if she had grown up often drinking stream water (along with well water, which would be cleaner) would it still be necessary to boil water, etc.?
If it rained would she collect rain water to avoid having to boil stream water?
ETA: The apocalypse happened about 4 generations ago, so rain water is ok (y'all helped me with that one earlier ^_^)