Don't be harsh on the OP. You guys just don't understand what it is like to be OCD (not criticizing OP because I am OCD about my car
) about this stuff. Especially when you spend so much time polishing and getting the paint perfect.
OP, just tell her you appreciated the gesture, but it wasn't necessary for her to do that and you will take care of it yourself. If she really wants to make herself useful, get her to rake the leaves, and you can clean the bird crap off the trunk.