Who is Mildred Hanstable from The Cat Who Went Underground and what is their importance?

Mildred Hanstable is one of Qwill's friends. She is also Roger's mother-in-law. Mildred lives in Mooseville where she teaches school, writes for the local paper, raises money for the hospital, and conducts a non-profit project for low-income handworkers. Qwill spends a lot of time with Mildred, and she feeds his cats during his hospitalization.