Who is Teresa Guerra from One True Thing and what is their importance?

Teresa Guerra is Kate's nurse who visits three times a week to monitor Kate's blood pressure and to help her bathe. She is twenty-three years old, but is very serious about her job. Ellen claims that Teresa is a nurse / shrink, and that she too feels like Teresa's patient. Teresa is Ecuadorian and has had a difficult childhood. Her mother was struck and killed by a cab driver in New York. She is a constant source of friendship and support for Ellen during the final months of her mother's life, and during the court proceedings.