It,s always difficult when you have the "neighbour from hell who hates cats" living next door to you
I had one like that when i lived in Braintree (many years ago)he too threatned to poison them if he caught them in his overgrown weed patch that he called a garden
Trouble is he carried out his threat and did poison one of my cats

I had the police round and also reported him to RSPCA (not that they did anything)but as nothing could be proved he got away with it

luckily my vet was able to save my cat but i wouldn't/couldn't trust him after that and so we moved away
I would suggest the water pistol treatment (it won,t hurt your cats and may keep them out of her erm...garden
