I've name changed for this and posting on behalf of my mum.
Several years ago people moved in to the adjoining (attached) property and replaced the original fence in the back garden. The fence had become damaged on one or two panels by a wisteria plant in my mum's garden that had been there about 10 years. The fence is 5 or 6 panels in total. So the new neighbours replaced the fence themselves with little consultation about it but all fine. The wisteria died and was not replaced. Fast forward a few years and there's now a clematis growing next to the fence that needs supporting. Mum's gardener has attached a wire support to the mum's side of the fence for the clematis. The wire support does not protrude above the top of the fence so the neighbours can't actually see it. When the gardener was doing this the neighbour came out of the house and started shouting and being aggressive about it and was deeply unpleasant. They were reassured that the plant would not damage the fence because the support would mean it doesn't grow through the fence and the gardener would be maintaining it. The neighbour kept coming out ranting and raving saying mum and me had attitudes and accusing me of blanking her in the street and slamming the door despite the reassurances. Until that day I wouldn't have known her if I had passed her in the street anyway.
The following day the neighbour stopped at the top of mum's drive and glared down it making mum feel uncomfortable.
Today mum has had a letter through the door demanding the support be taken down and saying they don't give permission for a large plant to be be grown against the fence. It's a clematis, it's not a large plant. They have claimed they tried to be reasonable and discuss the matter but the incident the other day was the first we knew of any issues and they came out of the house shouting and being aggressive in that manner.
They have threatened legal action and my mum is really upset. She's disabled and elderly and now feeling very anxious and intimidated by the neighbours.
I haven't told her but they also have one of those blink type cameras pointing into her garden. All they'll see is washing being hung out so I've no idea what they have done that for.
Any advice much appreciated.