Typically her drawings are sketched in pencil, then smudge shaded with a tortillian, then inked with a very fine ball point pen, then colored with grayscale prisma color markers and finally taken into photoshop where she works all manner of dark magics on it that I have very little comprehension of.
The water color look that she does sometimes is actually just her marker technique.
In all fairness, my wife has been doing art and drawing for a very long time, attended art school for over 2 years and is currently working on her portfolio so she can get a job doing art/animation professionally.
I'm also trying to talk her into doing lots more Planescape themed art 
Mmmm - can your wife give us some more 'doodles'? B/c this ain't just any 'doodle'.
Actually, in looking over the deviant art page - I'm curious, for a lot of the ink/marker sort of sketches she has in there. Are those ink, marker, or watercolor, or digital? She doesn't seem to have many comments answering *how* she went about getting that particular look of dark fuzzy lines, and watery textured background colors.