Encouraged by Polly's comments I made another attempt to find Louisa Cruwys, junior, the daughter of Henry Cruwys and Louisa Hartell, in the censuses, this time with much success. I found that in 1851 Louisa was a schoolmistress living in Wilton, Somerset. For once her name was actually spelt and indexed correctly. As it is such a rarity to find the name spelt correctly in the censuses I had been searching for all sorts of complicated permutations but had restricted my searches to Devon and had not thought of looking in Somerset. In both 1861 and 1871 Louisa was a housekeeper working for William Pattison, a hotelkeeper, at the Castle Hotel, North Street, Taunton. Finding Louisa in the 1871 census was a particular challenge and I had almost given up when I finally stumbled across a mysterious "Le Crump" in the indexes, which turned out to be Louisa (her name was written on the census page as Le Cruwys)! By 1881 Louisa was a hotelkeeper in her own right running the Luttrell Arms Hotel in Dunster. She died in December 1882. Intriguingly the National Probate Indexes show that she left a substantial estate valued at over £1,000. William Pattison did not marry so it seems a distinct possibility that he died young and left his business to Louisa, his faithful housekeeper.
See also Louisa Cruwys postscript.