Little bit of a back story to this. I moved in just over a year ago and didn't seem to have any problems at all with neighbour next door. Three months ago I had a knock at the door from the police, they searched my home and stated that the said neighbour had made continuous phone calls reporting that my home was some sort of cannabis factory!
No cannabis here I'm afraid. The police officers said that she clearly isn't mentally well and said they would refer her to the mental health unit - I've said nothing and not seen the neighbour up until 3 days ago.
I have two sons, 7 and 8 who play football in our garden, she has kept their balls by her back door which I thought was strange, why not throw them back over?
The children were in the garden and myself in the kitchen. They asked for their balls politely to which she replied "no"! I heard that came out and said erm, hello? Can you please give their footballs back, then she replied no, and if they keep coming here I will be throwing them in the electric box (an area behind both our gardens with large high voltage warning signs) she claims the ball hit her back door and made her jump when she was in her kitchen and fears one of the balls will damage her water feature. I've got very ranty saying they are children and the reason she is keeping them is because the police left here empty handed. She told me I must have gotten 'whiff' of them coming so I removed all the drugs!! 
anyhow later that evening she threw them back over.
Upon speaking to the person that lived here before she had done the EXACT same thing and she made his life hell as far as I'm aware, continuous calls to the police about a cannabis factory!! Coincident?
I have called the housing on the first instance when the police came around and never heard back from them. I have called again to explain about the children's balls but I fear it will fall on deaf ears again.
Anyhow, yesterday my eldest son was bouncing on the trampoline and came running in to tell me she was sticking her middle finger up at him through her window!!! At which point I just don't know what to do so I told of him to come inside and we went off to our party.
Today one of the balls went back over her garden, whilst the children were in the garden she came straight out shouted at my two sons "piss off you mother fuckers" and yes, threw the ball into the electric box area so it cannot be retrieved! They've ran inside to tell me as I'm making my way through downstairs to go into the garden I hear her screeching at the top of her lungs "evil fucking mother" literally screamed! By the time I've opened the garden door she has gone inside and slammed hers.
What do I do?!!!!