Great thread TidyDancer! I'm with the keep cool and don't let her hold sour grapes over you group. She does sound a bit, how would you put it, unaware? So something like
Dear friend (ahem)
I would have loved to have helped you but I'm a bit stretched that week. Can't wait to see the photos!
Best wishes
Tidy
Leave her nothing to get a horrid painted hook into.