I noticed a newspaper sticking out of her letterbox after taking DS for his swimming lesson, paper had probably been there for an hour or so I reckon. Then when my parents came about 6pm for tea and my dad remarked about the paper and that there were no lights on in the house. Checked again when they left (about 11pm ish), paper still there and no lights. I don't know whether to knock on tomorrow if it's still there and if I do shall I call in the morning or leave it 'til the afternoon or not call at all? She could be ill in bed or equally she could have had a fall or something.
Here's the backstory in case you're wondering why I am deliberating and not just doing it;
She pretty much keeps herself to herself but is getting frail now, physically and mentally. She has history of accusing people of trying to poison her etc when they have been invited in at her request to help her with something, and has previously accused us of being someone else (previous owner of our house we think) and of hooking up our electric to hers plus various other confused exchanges.
I feel really sorry for her as she obviously gets a bit confused sometimes and she's all alone in the house (although does go into town on the bus occasionally). She has form for ringing the police for various things and when DH spoke to them last summer they warned that social services etc were involved and for us to not get too drawn into helping her etc due to her making stuff up and accusing people of various things.
My dad was making jokes about having a sniff at the letterbox 
but what if something has happened to her?!