Who is Sylvia Foster, Ruth's grandmother from Housekeeping and what is their importance?

Sylvia is Ruth's grandmother. It was Sylvia's husband who built the house, around which. Ruth's story is told. Ruth doesn't meet her grandmother until she is well into her seventies, but even in her seventies, Sylvia remains an active, nurturing woman, who is well able to care for her house, as well as those living in it.