A neighbor who feeds a visiting cat is usually being kind, not careless, and the conversation goes better when it starts from that assumption. Your cat, meanwhile, is working a second route she has built herself: a meal at home measured for a vet-directed diet, followed by a top-up two gardens away that quietly cancels the measuring. What you need from the neighbor is not an apology but a change in one habit, and people change a habit far more readily when they are thanked for the intention, given a clear reason, and offered another way to keep the friendship with the cat that they plainly enjoy.
The Conversation Itself, Friendly and Factual
Choose a relaxed moment rather than catching them bowl in hand, and keep the points plain and factual. Say that she is on a diet your vet has directed for her health, that food outside that plan genuinely works against it even in small amounts, and that you are asking every neighbor she visits, not singling them out. You do not need to explain the medical background, offer a detailed history, or produce documents; her diet is a household fact you are entitled to state simply. Make the request itself unmistakable — please do not feed her anything, treats included — because a kind person who hears only concern may assume a smaller portion solves it.
A Replacement Way for the Neighbor to Stay Friends
A flat refusal can leave a neighbor feeling shut out of a small pleasure, so hand them a permitted version of it. If her plan allows treats at all, supply a small pot of approved treats yourself, explaining that these are counted within her day, and refresh the pot occasionally so the supply stays yours to control. If treats are off the plan entirely, offer garden fuss instead: she will happily take stroking, company on a bench, and a game with a leaf on a string from a person she likes. Fresh water in hot weather is a kindness you can usually accept, provided the neighbor checks with you first rather than improvising meals.
When a Note Through the Door Works Better
Some neighbors are rarely seen, some conversations get awkward, and some people absorb a request better in writing. A short note through the door is a sound backup, not a threat: thanks for looking out for her, she is following a diet set by your vet, please do not feed her, and here is how to reach you if she ever seems unwell or shut out. Keep the tone identical to the spoken version, since a note that reads sterner than you sound can sour a good relationship. If you have already spoken and feeding restarts, a note also gives you a dated record that the request was made clearly and kindly.
Holding the Line at Home While It Settles
Help the agreement work from your side. During the hours when the neighbor usually feeds her, keep her indoors while the new understanding settles, since a cat standing hopefully at the usual hour is a hard test of anyone's resolve. Make sure everyone in your own household repeats the same message if the neighbor raises it with them, so she is not re-offered food by a family member who has not heard the plan. Watch her weight and condition as your evidence: if she keeps gaining despite the conversation, revisit it politely with that observation in hand and ask your vet whether anything else in her routine needs adjusting. One voice from the household keeps the request credible, and that is what Family Sharing in KinsLe provides: a shared view of her diet details for every member who might meet the neighbor next.