Dungeon Siege: Throne of Agony

I'm not entirely certain, but I think you're referring to the quest where you go to the corrupted forest (or corrupted woods, w/e) and are supposed to cure 4 corrupted trees.

It doesn't show on your map but if you look around you can find some trees that are twisted and black, 'use' the water on them and they should change back. Sorry if I gave a wrong answer.

You can find the corrupted while doing the quest Bloodshadow, it is near the end of act 1 so there's no need to rush to it.

Like auraziel said its on the very end of chapter 1 u cant miss it...

Walk through "The Temple of the Earth" and you'll find her at the exit.