Who is Mrs. Thornton from North and South and what is their importance?

Mrs. Thornton is John Thornton's mother. She likes to come across as a strong figure in appearance and personality. When a stone hits Margaret in the head, Mrs. Thornton braves the angry crowds to fetch a doctor. Yet this act is not necessarily done out of pure kindness and actually she hates Margaret for both for turning down her son's love and because she originates from the south. At one stage, Gaskell claims Mrs. Thornton would have liked Margaret if she had originated from Milton.