There are a number of ways to resolve this issue in a responsible and satisfactory way, we are meant to be professionals and need to adhere to codes of conduct when dealing with customers/members of the public.
Sometimes this can seem like an uphill struggle, maybe even a pain in the arse and almost always an inconvenience, but try we must.
I think the thing to do is to make an appointment by phone to go round and inspect the damage that your guys are meant to have caused, on the way pop into the local garden centre and purchase a pack of grass seed. On arrival when the customer isn't looking generously sprinkle the grass seed into one of her hanging basket displays, this'll readily screw her display of top-notch petunias once she waters them again, which is likely to be shortly as we're currently experiencing a dry spell.
Next time you visit the road you'll be able to admire your handiwork as her hanging basket will now be displaying a most admirable lawn; and more importantly she wont have a bleedin' clue.
Matt