If you can read this, then…What would you do?

Here’s the thing. We bought our house 9 years ago. Before we bought it, no one had lived in it for 7 years. The man who had lived there before us was an alcoholic. He died there from drinking (he was relatively young) and was discovered by my nosey next-door neighbors, dead on the basement stairs.
When we came to view the house with the real estate agent, she had to get the keys from the nosey next door neighbors, Mr and Mrs S. These neighbors are in their 70’s and have children in their 50’s. They accompanied us uninvited on the tour of the house and land. They seemed genuinely pleased when we bought our house and said they were glad to have some life back in the place. They seemed a bit up in our business (accompanying all work crews uninvited), but we figured nosey neighbors were better than indifferent ones.
Mr and Mrs S. had been using our land and had been keeping their chickens in our chicken coop for years before we bought the place and were none too pleased to have to evacuate their chickens. I understood them because chickens stink and they didn’t want to mess up their lovely yard. But what’s mine is mine so…the chickens remained(???). I even joked that chickens in my yard were in danger of finding their way into my Sunday rosół. The chickens still remained. Eventually we had to tear down the chicken coop to facilitate the chickens’ exit. Mrs S. was happy to take all the wood from the tear-down, so no hard feelings, I guess.
Mrs S. and I have nothing in common, let’s face it, but we used to have nice chats over the fence. She’s very opinionated as older village ladies (of any nationality) can be, but my power to ignore her comments (pretending I didn’t understand) was always strong. C’mon we have to find a way to get along with our closest neighbors despite our differences. It just takes a bit of goodwill on both sides (or a lot of goodwill on one side). There was so much goodwill between us that we even have a door in the fence between our properties. We don’t use it. Ok we used it once, invited, and the neighbor’s dog promptly bit Misiu on the leg.
9 years ago, before we had done any work on our house and before the house was livable (in my opinion livable, somebody had lived there without water or electricity) Mrs S. asked if she could collect stinging nettle from our neglected garden for her chickens. We agreed then. Our house and garden are now maintained. There’s no stinging nettle, hence no need to enter our garden. Oh, except for the pears. The pears which hang over into our garden with the rotten pears I have to clean up each year. The good pears mysteriously disappear from the overhanging branches each and every year. Once we even met our neighbor and their children in our garden removing the pears. They gave us a tepid dzien dobry, did not speak to us, treated us as intruders, did not high tail it out of our garden and did not even offer us a pear.
So after a recent hubbub on our street in which we were told by the neighbor that we should go back to where ever it is we are from and that we have no right to an opinion because we have only owned our house for a year (we’ve owned it for 9 years and lived in it for the last 5), we were prepared for a pear fight this season. There’ll be no pear fight, of course, as the pears have been cleaned out in our absence.
So here’s the thing. I don’t care about the pears. But since then I have been made aware that this neighbor enters my garden on a regular basis. I have photos. The suspicious fartuch is clearly visible. I even have photos of Mrs S. standing in my yard, leaning on my fence, talking to another neighbor. The pictures are from many different days we know not only from the date but from the rotation of fartuchy. The person who took the pictures says that my neighbor does no harm and they cannot in fact figure out why she enters our garden in the first place. It is not to check that everything is ok. We have not spoken for months since we were so rudely treated by her and her children. (The rude incident while not initially involving us took place on our land and involved the police)
And now I am wondering how to address this issue. It would be difficult for me to lock all entrances to my garden. And the real issue is, I don’t just want to say, “Hey, I know you come to my garden when I am not here. Please stop.” because honestly, where is the fun in that? I thought about writing a sign and leaving in the yard that says, “Mrs, S, if you or your son or daughter can read this, then spier…” but I think that’s too aggressive especially considering her age. What should I do?