I was biting my tongue while thinking about weed seeds mixed with clay and rolled into little weed-seed-balls .... a slingshot ...
... but that would have been WRONG!
I think my neighbor also has OCD or "neat-freak" or "control" issues. The first and only thing she did in her yard was to have someone kill everything she could afford to kill.
Sometimes she sends her husband out with a nylon-line weed-whacker, and he trims the feeble weeds and grass down to the clay line, and then sends up a cloud of dust.
To be fair to her, my yard IS messy. If she had not gone so far out of her way to make trouble for me, I wouldn't feel so gleeful and "serves you right"!
Back when she was pretending to be a gardener, she talked about bringing in workmen to create a Square Foot Garden. Her eyes glowed when she talked about how "orderly" and "controlled" it would be. She must have thoguht that each plant would stop growing when its leaves touched the imaginary line bordering each square from the next square. To HER, "imaginary" lines are real.
I think what she really needs is concrete with thin white lines painted on it. Maybe pictures of plants - pictures that are very UNIFORM in size and shape!