Who is Grandma Wolf from Private Peaceful and what is their importance?

Grandma Wolf, actually the Peaceful's great aunt, was the closest thing to a real grandmother they had. She insisted on being called Grandma, and she is described as old and mean.

When Thomas's mother went to work for the Colonel's wife, Grandma Wolf came to live with them. She was a strict and often punished the boys without even telling them why.