I have a cat and I think it's ok for your neighbour to use the hose, it does no long term damage to the cat. I have used water myself to deter the cat that was bullying mine. I also use water to deter mine from walking on the work surfaces when she was kitten, I don't even have to spray her anymore the sight of the blue spray bottle when she's thinking of jumping up there/scratching the furniture makes her stop and come to me for strokes ( as if to say I know I was being naughty but I do love you :-)) Be thankful the neighbour is only using water, some people use more excessive and fatal means, my cousin's cat was killed by being poisoned with anti-freeze.