Arlen worked with Ephron again on the 1989 film Cookie and also co-wrote the script for 2007's Then She Found Me.
Released in 1983, Silkwood told of a plutonium plant employee who died in suspicious circumstances while trying to uncover wrongdoing at her workplace.
Arlen, who was born into a family of journalists, also wrote biographies.
One of these - about her aunt Alicia Patterson, founder of the New York newspaper Newsday - will be published in August.
Arlen started out as a journalist herself and worked as a film editor in New York before collaborating with Ephron on the Karen Silkwood drama.
Mike Nichols's film was nominated for five Oscars in all, though it ultimately left the 1984 Academy Awards empty-handed.
Arlen's other writing credits included Louis Malle's 1985 film Alamo Bay and 2000's The Weight of Water, which Kathryn Bigelow directed.
According to her second husband, the writer Michael J Arlen, she died in Manhattan on Monday after a long illness.
Alice Arlen, the US screenwriter who collaborated with Nora Ephron on the Oscar-nominated screenplay for Meryl Streep film Silkwood, has died aged 75.