Miss Thornton lives at Crag Gill; she is the only contemporary of the Great Aunt left, but “she (the GA) had a row with her ages ago. They haven’t been on speaking terms for years”. So there is no danger of her giving the Ds away to the GA, as Nancy tells the Doctor (PM8). Later the GA alights from a butcher’s van, rather than being seen by Miss Thornton in the front seat of the van (PM23).