Ms. Colvin made her stand on March 2, 1955, and Mrs. Parks made hers on Dec. 1 that same year. Somehow, as Mrs. Parks became one of Time Magazine’s 100 most important people of the 20th century, and streets and schools were named after her, Ms. Colvin managed to let go of any bitterness. After Ms. Colvin was arrested, Mrs. Parks, a seasoned N.A.A.C.P. official, sometimes let her spend the night at her apartment. Ms. Colvin remembers her as a reserved but kindly woman who fixed her snacks of peanut butter on Ritz crackers.