Who is Mrs. Karafilis from The Virgin Suicides and what is their importance?

Mrs. Karafilis is the grandmother of neighborhood teen Demo Karafilis. She lives in the basement of the Karafilis house. Her dramatic experience as a survivor of a Turkish massacre during her youth led her to despise the American lifestyle. Consequently, she displays very little interest for the suburban life that surrounds her. Mrs. Karafilis nonetheless cares for the Lisbon girls' fate. She sympathizes with them and says that their suicidal attitude isn't surprising. This leads the narrators to suspect that she and the Lisbon girls either communicate secretly or share a common outlook on life at a deeper level.