On Sun, 15 Jul 2007 10:41:32 -0500, Lar wrote:

I would guess her garden is under an oak tree... have her look up
Jumping Oak Gall. Interesting little creature that can appear time to
time when conditions are right. There is a tiny wasp larvae inside.

You would guess right! I looked it up myself, and it did appear to
match the description and the video. When I told her, she confirmed
that there is an oak tree over her house whose droppings would slide
off the roof onto this one particular place.

Thank you -- I'm just about sure that you have solved the mystery.