dealing with an unstable neighbour

My 68 year old mother has a mentally disturbed neighbour who has just moved in next door. Her unit over looks mum's yard and every now and then, when mum ventures into the yard the neighbour will yell nonsensical abuse at her. I told mum to ignore her as I thought it may make the neighbour fixate on her but it hasn't made any difference. The neighbour, sometimes dressed in a silver, mask has been on mum's front lawn taking photos of her house. She has also stated that she is the president of the CIA. Mum is obviously very concerned.What should mum do? ignore her or try to reason with her or what?
Steve Daniel

The neighbour is obviously mentally ill. To reason with her will hardly do you any good since she has her own look on reality. The best thing that you mother can do in order not to antagonize her neighbour is to try and look beyond her beaviour as much as possible.