When my elderly mother was alive, the neighbor would come onto our property and leave tuna out UNDER a crawl space of my mother's back porch. Not only did my poor mother get cats, she got raccoons, which decided to habitate there. She couldn't figure out what was happening. When the last raccoon died, the cats lived there and by the time my mother died and we took over the house, the stench was AWFUL! We decided to put lattice around the crawl space under the porch to end the problem and my neighbor came onto our property and told the contractor he couldn't do that because there were animals who were trapped by the lattice. He created a one-way out flap door with a lure of tuna to get them out and she, in the night, rigged the flap-door so that they could still come and go. I was ready to get a restraining order against her but everyone in the town was so golly-shucks about her being crazy--I have paid the price of a nut for a neighbor. This spring we painted the house and the cats urinated all over the painters' drop cloths, ruining them. When we are there on the weekends the cats hop all over our cars, getting them dusty with footprints.
It has become an untenable situation. Three weeks of pepper would be a small price to pay to be rid of the cats--if only I could get rid of the neighbor.
You may want to sprinkle some on your neighbor as well ;’}
I wish you the best of luck!