Who is Mrs. Canty from The Prince and the Pauper and what is their importance?

Tom's mother, Mrs. Canty, is described as a warm, loving, humble and gentle woman who loves her son, but is unable to stop her husband from beating him. The family has so little to eat that Mrs. Canty gives Tom her own food. When she later sees Tom in a procession, she recognizes him by a gesture. Tom, however, denies knowing her, something that causes him immediate grief. Mrs. Canty does not hold it against him.