We have a neighbour who we suspect has dementia.
It all started in September when I got up to find a note posted through my door asking up "to keep the noise down as we were depriving an old lady from her sleep." I immediately went next door and "apologised" for any noise, and suspiciously asked what noise (I thought it was possibly the tv was a little loud in the evenings although it is off by 10 pm), however she told me it was a noise at 2 am and kept repeating to me "you know what I'm on about, just stop it!" She then went on to tell me our daughter is noisy as well playing on her bike on the landings during the night she couldn't think what a bike was called, she described it as a toy with two wheels. The problem with this accusation is we don't have children, I told her this in the nicest possible way she just shouted liar at me a few times then shut the door in my face.

Since then we have had plenty of nights were she stamps around, bangs on walks etc. And the latest ones are putting her music on full throughout the night, hoovering in the early hours and last night she started shouting. We have two dogs so whenever the neighbour is being disruptive they are barking to alert us, of course we can't get mad at them as they are doing the right thing in alerting us to any strange goings on. But it is seriously disrupting our sleep as we are having to go down to settle them so they know they are doing right.

The neighbour has informed us that the noises "we are playing" are recordings of an oxygen task that "the previous resident" had done - we know the previous residents daughter and she has said there's nothing of the sort, so it makes me wonder how long this as been going on - of moved to this property in April.

The neighbour has one sister who is aware of this (apart from the latest shouting, radio and hoovering) but she's the only person the neighbour has and she's acting normal sound her so she can't bring anything up with her, as of course she doesn't want her to block her out. I have contacted her doctor who has listened to me on several occasions but has said he can't do anything unless she agrees or until it gets worse.
Our neighbour has threatened to get in touch with council to report "our" noise.
Is there anything any of you could suggest we could do as we're not getting much sleep lately and I don't know who else to turn to? Should I write her a letter, call the police or get back in touch with the doctor and ask for something to be done? I contacted social services before her doctor and they informed me they can't do anything.