How to deal with elderly person who sucks the joy out of life

Second the one-way film, I'm going to put some up. You'd need to close curtains at night though
Not sure what you can do about banging on the door though, unless you put up a ring doorbell and spoke to her through that
Do you think that agreeing to phone once a day, every couple of days whatever for 10 mins or whatever you could cope with might be helpful, and reminding her of your boundaries with not wanting to be always hearing about the stuff that bugs you so much
Might local Age UK or other such befrienders ring her occasionally [but obviously they would need to agree it with her .
We all need to moan every so often but most of us manage to not piss the listener off

I think that some of this depends on the exact relationship around her being in the 'granny flat'. Do either of you 'owe' the other something, financial or emotional? It's difficult to handle firmly until you are clear about that.
In normal times, banging on the door and looking in windows would make me wonder about dementia - but all sorts of mental health problems are raised by this situation.
That behaviour also makes me think that she is feeling anxious. I would, if you can, work on making her feel a bit better, then say that you need some rules.
Just saw a cross post about dementia!

I would say to her, while I don’t mind helping you with things, All this worrying is not going to help anything is it, worry helps no one, some people love to moan( I must admit does my head in) but I do wonder if she has the start of dementia, I must admit I wouldn’t put up with the constantly banging on my door and certainly not peering through my windows, not a lot you can do, just speak to her kindly but firmly, she may not be aware she is annoying you,

Sit her down, give her a cup of tea and then as kindly as you can explain the problem. How miserable it makes you feel and what you have decided to do to sort the problem out.

This could be limiting what you can do for her, give her a written list, see her at specific times only except in the case of a 999 emergency. Say that conversation is not to be about anything in the news, unless it is positive and that she is to stop looking through your windows.

Do this firmly and clearly. Whether she listens to you, takes what you say on board or believes you is her problem. Then live life firmly to the rules you have set and just tell her every time she trangresses, that she is doing so and you can discuss any problem at your next planned time.

I can see no point in pussyfooting in circumstances. Tell her firmly, but kindly, and then implement the new rules firmly but kindly. She will eventually get the message.

AnnieMae123, also, do bear in mind that doing too much for an elderly person is really not good for them, either.

They need to stay as independent as possible, do as much as they can manage - and exercise, not sit in a chair making demands!

Perhaps your aunt's mind is beginning to fail her. It seems strange that she regularly looks through your windows.

I think it might be an idea to try and calmly discuss the situation with her but I suppose you've already tried that.

AnnieMae, you wrote:
"No matter what I do for her it is never enough and she brings me down. "

You are the one who can and should decide when it is enough.

Have you ever told her " I will keep helping you if you stop troubling me with your unceasing worrying".

Unless she is demented she will understand such a simple statement.
It is kinder to be candid than to stop talking to her with no explanation.

I think I’d just say (assuming you’re at hers and not the other way around) ‘I’m sorry, but if you’re just going to be a Moaning Minnie, I’m going home. It makes me depressed.’

If she comes to you (and you feel like answering the door) I’d say, ‘I hope you’re in a good mood - I really don’t want to hear any moaning.’

And I’d tell her very firmly NOT to bang on doors or peer in windows. All a lot easier said than done, I know - some old people can become so demanding and almost tyrannical, and we can dread upsetting them because of tears/sulks/major strops.

When between us we were coping with 3 of them, my elder sister (who is rather more patient and polite than I am) once said with feeling, ‘I’m sick of bloody old ladies!!’

I’m sure some of us can relate to that!

You can get window film that you can put on the windows, you can get a type that you can see out of but nobody can see in. It isn’t permanent, easy to remove but it may deter her from looking in your windows. If you have come to this arrangement out of kindness because you are the only one in the family to take responsibility for her that is admirable but I think you need to establish some ground rules as Grandmabatty suggests. We had my mother to live with us for five years out of concern for her safety. It wasn’t ideal because she was also a very negative, glass-half-empty person, the one thing we underestimated was our loss of privacy and it was a big issue so I do understand how you are feeling. When restrictions are lifted you will be able to go out more and get away from the situation.

These are odd times we live in and lock down, if you live in UK, can exacerbate people's worries. Are you her only family and is that why she's constantly harassing you? Because peering in windows and banging on doors is harassment. Actively practise not listening to her moaning and give vague answers. Limit your time with her. If ten minutes is all you can bear, then ten minutes it is. Tell her when you will visit her. Go to the toilet if necessary to avoid having to engage. I know some will say ignore the peering in windows but it is difficult to do when you are not used to it. If she brings it up, explain that you are visiting her but it will stop if she keeps behaving that way. It must be very exhausting.

Doh, , should read ‘It’s time to change...’ etc

It’s time to your own behaviour to change hers. Do you you bite your tongue when she brings you down? Answer back in future and say if what you’re doing isn’t good enough, it’s fine by you, you won’t do it for her again. My FIL criticised the meal I served up one day. There wasn’t anything wrong with it. I told him ‘fine, I won’t cook for you again and put you through misery’. He shut up then and there.

AnnieMae123, I second not answering the door. You are not at her beck and call. Perhaps she can text you if she needs something? Maybe your hearing is not too good - so you need to arrange other ways to communicate?

Stand up for yourself - and laugh at her (it works, believe me). Say 'Oh, you're so funny!' at every opportunity. It really does help if you laugh and make light of things.

If you haven`t got net curtains,get some,she can`t see you then.
And don`t answer the door.
She could be lonely and looking for problems to moan about too.

How horrible AnnieMae - I had a neighbour like this but luckily I wasn’t “responsible” for her.
Is it your flat or is she co-incidentally next door?
Are you working? And how able is she?

Looking in the windows is really invasive. I know because we used to have this too. Is it possible to make peering in harder somehow or can she get all round the house?
Do you have a private garden space?

If you are near a town, do they have any social groups you can introduce her to once the lockdown is over? You need to know that some days she’s out!

Are you obligated to her or could you move?

Is there a possibility of moving? ?

Very hard for you, some people seem to thrive on complaining about everything, it is what keeps them going! You can tell her it upsets you that she can never talk about anything positively, but I doubt it will change her for long. Banging on your door is another matter, you can ask her not to do it unless it is an emergency, and give her weekly dates to let her vent, but I doubt if she would stick to them. Actually, is there any way you could move?

My mother always used to day to me, "laugh and the world laughs with you' cry and you cry alone". There is some truth in that.

Can you find some comedy acts on TV for her? Maybe cheer her up?

Move house perhaps ? Or if that isn’t possible maybe turn music on so you can’t hear her. Not all the time, just when you’ve had enough! Actually, to be truthful, I would just tell her bluntly. You might have to put up with weeping and gnashing of teeth but it might just do the trick!