Poo Picasso?

Gday. Im looking for some advice on behalf of my SIL. Her DD ( 3yrs start of May) has been expressing her arty side, by fingerpainting with her own poo ! It's seriously disgusting, and causing all sorts of issues re discipline etc. SIl doesnt know what to do. Now her DD is a pretty (OK very) full on toddler. Id go so far as to suspect she has ADHD. She never sits still, tears around the house at a million miles an hour, crashes into walls, furniture and people with great force, and constantly squeals at the top her voice. She is also very rough with other kids. Now this poo thing started as an occassional thing about 6 months ago, and is now weekly or more. She smears poo on the floor, doors, walls upholstered furniture, you name it, then laughs!! So far they've tried time outs, banning her favourite tv shows, taking away her toys, and smacking, all of which have been totally ineffective. IMO it's an attention thing, and maybe shes ready for TT, but what do you think? Anyone come across this, and what did you do? I feel bad for them, they're trying, but it's getting them nowhere.:wall:
BTW about the ADHD, her dad was the same as a child, and was on Ritalin at an early age, so I think that genetics may play a part. Doesn't help with the behaviour issues though. Any ideas would be great, and I'll pass them along.:D

As far as I know, it's not uncommon for kids to experiment with their own personal paint supply LOL But seriously, if they are having all these other issues with her as well, and there is a family history, maybe a trip to the paed would be a good idea. It does sound a little worse than your average poop play, and not at all hygenic for anyone.
Hope they are able to sort something out soon.