Who is Leslie from Brothers and Keepers: A Memoir and what is their importance?

Leslie is Robby's new girlfriend by the end of the book. She is half black and half white. She looks white. She has blond hair, green eyes and light skin. She has had a rough childhood and she is addicted to heroin. Robby helps her kick her drug habit. Leslie thinks Robby will be out of prison in a couple years, but he does not have the heart to tell her the truth.