The legal disclaimer at the end of the film (which, for most films, merely states that all characters and events are fictional, with any real-life similarities being coincidence), notes that the character of Penny Lane was "loosely based" on a real individual.
Cameron Crowe has stated that Penny Lane is based on his real-life friend, Pennie Trumble, who goes by the name "Pennie Lane". She lives in Portland, Oregon, and is involved in the music industry.