It's obviously loosely based on Jennifer's relationship with her older sister, Carrie. Dressed up and changed to fictionalize it, but very similar. Carrie had problems growing up, ran away and became a drug user. She's clean now. Jennifer, who was only 2 when her parents divorced, didn't have as many memories of their father, Vic Morrow as Carrie did. It was Carrie who became close to Vic in his last years, while he and Jennifer were estranged. But, Jennifer was, in her own words, "A good kid", and loves expressing her emotions through acting.
I remember reading about this back when the movie came out. The writer (their mother) fictionalized the roles, making Georgia a successful musician. In real life, JJL was the 'Georgia' character.....a successful actress from almost the beginning of her career, talented, and very focused. Her sister, Carrie, was not the talent that JJL was and had a bad drug/drinking problem.
The bad news is you have houseguests. There is no good news.
I heard Jennifer Jason Leigh and Mare Winningham were very close friends. They look like they could be sisters. I confused them a little early in their careers. I think it was partly because both of them seem to play prostitutes and/or drug addicts fairly regularly.