I had the worst ‘neighbour’ previously diagonally over the back so our properties weren’t even adjacent. Without going in to too many details, it turned out she was obsessed with me for 2 years and was having delusions about me (I can only assume she was paranoid schizophrenic, it just doesn’t make any sense otherwise). Lots of strange and unpleasant things happened (eg she smashed a window in the middle of the night while I was asleep) but it took me a while to piece everything together as I had literally done nothing and barely had any contact with her aside from some weird interactions in the street, at my door and at the shops.
It culminated in her screaming and threatening me at the local shops in the carpark while I stood there silent, confused and mortified all in one, holding my (at the time) 2 year old. I ended up selling the house days after that to get away from her, it was awful and I was terrified by that point.
Luckily my new neighbours are quiet and friendly, and keep to themselves. It was literally just the worst luck ever being near her and becoming the focus of her delusions.