The water/shockproof cams have come a long way, but they still struggle mightily in poor light.
Small enough to fit in a pocket is a challenge.
The best pocketable camera right now is probably the Canon S110. The older S100 and S90 are wonderful as well.
I love my Fujifilm X10, but it isn't quite pocketable. Jacket pocket, maybe. The recently announced XF1 may work for her.
As for durability, find a small pelican case that it fits in for the heaviest duty work, and a even a stretchy neoprene sleeve type case will protect it without taking up additional space in a camelback/purse/whatever.