Basically I've lived here for 15 years and share a hedge with my neighbour which she has always gone overboard decorating at Christmas time.
There was an issue 2 years ago with the back wall separating our gardens, it was found out that side of the house was our responsibility, fair enough we had the wall knocked down and replaced, they didn't offer anything. They then a few months later were asking us to go halves to have the hedge in the front taken out and replaced with a wall - this led to lots of laughing at how bleeding cheeky they were between me and dp (especially as they hadn't offered anything towards the cost of having the back wall done!) but we pointed out to them that it was our side of the house and our hedge so not their choice to make, they were ok with this.
So every year she decorates her house with anything available that's tacky (Some are ok but its the sheer volume I struggle with, I'm sure you could see her garden from space. I'm not just talking about nice little lights, she has them up the garden path, draped on anything that sits still in her garden for long enough
She says its for the "kids" - her youngest is 21 
. So last year she gets out the stupid hedge lights, they didn't work. I saw her struggling with them so we got chatting, I said oh maybe just leave them this year, be nice to maybe do something for ourselves in our side of garden anyway, as we had a ds who was getting into the lights and Christmas thing, so in the end we had our side decorated in our lights and she had none, I knew she was absolutely Fuming that she realised the hedge wasnt hers to decorate as she didnt talk to us for around 2 months - yes she is very, very petty, shes the type to put her wheely bin in her space if she goes out for 5 mins to stop anyone else parking there!
You can set your clock by her usually, 1st December she will be out putting up her works of art, but not this year, nooooo, she must of been seething all year round waiting for the day to claim back "her" hedge. Tonight i've come home to a multitude of colours of twinkling fairy lights draped haphazardly, glow in the dark sunflower heads and a light up reindeer on the top. The reindeer has since gone not sure where but why it didnt take the rest i dont know. The rest of the garden has been done too but i know she'll have more, its not even half of what she does usually, almost as if she wanted to get the hedge done first 
So what do I do, leave them, say nothing but put mine up next year in the summer to beat her.
Take them off my side and tell her they look a mess and i've hated this type of crap for the past 15 years, now I know its our hedge i dont want your crap on it.
Or just stick my stuff on top, I wouldnt mind if she just did her own side but the fact she seems to think i need glow in the dark sunflowers in my life gets me wound up.
I realise this is not a first wrld problem but the first year were having lots of new people over at christmas for dinner, I dont want there impressions of us to be a light up meerkat wearing a tie and holding a pipe 