On the 1841 census Mary and Jane Fletcher are recorded at Midgall St Liverpool, along with Thomas And Jacob Fletcher. I cannot locate in latter census records Jane and Mary. I am pretty sure DS located them for me some time ago and Mary and Jane Fletcher were listed as Mangle Keepers or Mangle for hire, not sure which. There was a collection for Mary when her husband died, for her to purchase a mangle, I suspect to keep the wolf from the door.
If it is any help, Mary died in Smithdown Road workhouse in 1873 which would narrow down the census. I have looked in FMP census records without success, but knowing me I've missed something.

As always, grateful for any help.
Gareth.