Tuesday afternoon I leafleted the area and discovered that letterboxes are evil!
Lots had horrid draft excluder brushes which tried to bite my hand and made it hard to get the leaflet through.
At 2am wednesday morning I went to feed the cats and me - I keep weird hours - and there she was, waiting for food. Fred was purring his head off, he loves his sis and has been depressed since she went missing. I fed them all, she ate a little but didn't seem particularly hungry. Maybe she's found food somewhere. Lots of people round here put out food for ferals, so it could be that; or maybe she's been living elsewhere and they found the leaflet?
Either the leaflets or the weather drove her home. I'm glad she is.
I'm grounding her for a week. Locked the cat flap and put out litter trays.
I can't find words for how relieved I am. I thought she might be dead or injured.
Thanks for the support.
I'm now informing all the sites I've put her on and Petlog and the vets.