I'd gently go on the defensive. You are allowed to have a life and you seems to be a considerate person. I can imagine you feel intimidated and may be a little bullied by your neighbours daughter.
So time for you to act on your own behalf, firmly, while being kind to your neighbour, who I suspect has some other issues going on.
You contact Environmental Health at your local council, explain your situation, what you have been accused of, your DD is your carer, DGC have to come with her due to lockdown, what you have in place to mitigate noise etc. Ask for a noise assessment.
This will help as you are most likely to have more complaints and you'll be able to state your case and defend yourself better if you've taken this action. If they then want to get the Police involved that will be Ok with you as I don't think there will be any grounds on which they can bring a legitimate complaint about you.
Once you have that in place if the daughter continues to accuse you of anything you have a case for bullying and harassment and as you are one of us "elderly" the police can get involved and speak to the daughter.
How she deals with her mothers issues is then down to her. May be her mother needs other help but that's not your responsibility.
From what you've said your noise is very reasonable and you are already doing as much as possible to reduce the noise. Please don't allow the peace and safety of and your home and family to be taken away by this.
I do feel for you as my sister has something similar a couple of years ago and it got to the point where she was terrified of loosing her home. Until she was away for a couple of days and was reported for having her music on very loud.
I go angry and asked the council for a noise assessment as we proved she'd be away at the time of that particular complaint. Sadly the person below her had mental health issues and for far too long was able to rob my sister of her peace and sense of safety.
Please don't let your situation get so bad that you get anxious or your DD's anxiety builds, these times are tough enough and we are all just doing the best we can.
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But sluttygran isn't doing anything remotely like that is she Peasblossom? Your extreme examples don't really have any relevance to the normal day to day living that the OP wants to be allowed to live in peace.