The piano in the Piano Lesson
Berniece is a strong independent black female that lives with her uncle and daughter Maretha. She is the sister of Boy Willie. She is attached to the piano and won't allow Boy Willie to sell the piano. She's a southerner, she won't let go of her dead husband's death. She's a very stubborn person.
Her most important line is "I don't want to hear that nonsense. Somebody down there pushing them people in their wells". The significance is why she moved up north to find a better life.