Who is Mom from Tender at the Bone: Growing Up at the Table and what is their importance?

Ruth's mother is neurotic and is later diagnosed with bipolar disorder. She is bohemian, wears no makeup and refuses to dye her gray hair. She is intelligent and has a PhD. Ruth's mother has lots of time and energy but not a lot to do. She is politely fired from several jobs as a magazine editor. The museum asks her to stop volunteering after she gives a risqué lecture on Picasso's personal life. She cooks for parties and brings home exotic foods like sea urchins and cactus fruit. One day she has workmen haul a huge, dead birch tree into the family's eleventh-floor apartment, insisting they can cut it to fit under the ceiling and festoon it with seasonal decorations.