I agree with the above- money is a tricky subject, but your dd does need to learn how to talk about it. Maybe there was a different understanding of what "clean the kitchen" means? (i.e. I would mean just wipe down the counters and load the dishwasher, but my DH would mean get out the mop and bucket and empty the fridge)
I think your instinct is right to stay out of it- money between friends can be twitchy.
MissMoosey had a good suggestion for an opening line- or something like: "OK so we agreed that if I do X, Y and Z it is worth $5 extra? Is there something special you wanted me to do that I didn't do last week? "
good luck, MKZ
did I say one project at a time?