Dornacker was born in Albuquerque, New Mexico, the daughter of John L. Dornacker. Her family lived at 1701 Las Lomas Road, NE Albuquerque, in a house built in 1928 by her grandfather, Dr Edward C. Matthews, a physician. She had two sisters, Ann and Mary. She was a performer from a young age, and wrote a six-act play while she was in Monte Vista Elementary School; at 8, she sang all the parts in an opera of her own composition "in a language no-one could understand".