She appeared in Francis Ford Coppola's You're a Big Boy Now as Barbara Darling, for which she was nominated for a second Golden Globe Award.

She attended Carnegie Mellon University in Pittsburgh, where she met her future husband, Gill Dennis, and spent her summers acting with the Kenley Players.

In 1964, Hartman was signed to play the ingénue lead in the comedy Everybody Out, the Castle is Sinking, which was not a success, however her performance was again positively received, and film producers took notice.

[9] In the early autumn of 1964, she was cast in the leading role in A Patch of Blue, opposite Sidney Poitier and Shelley Winters.

[14] Hartman won widespread critical acclaim for her performance, a fact proudly noted by the news media in her hometown, and was nominated for an Academy Award for Best Actress.

[18] In January 1967, columnist Dorothy Manners reported that Hartman had been cast in the role of Neely O'Hara in the movie version of Valley of the Dolls, beating out some more famous Hollywood actresses.

She had allegedly made a successful screen test winning over director Mark Robson and producer David Weisbart, the former already enthralled with her performance in You're a Big Boy Now.

[citation needed] Between the mid-1960s and early 1970s, Hartman appeared in three well-received films, two of which starred Broadway and Hollywood legend Geraldine Page, The Group (1966),[19] You're a Big Boy Now (1966),[20] and The Beguiled (1971).

[21] Portraying Pauline Mullins, the wife of former Sheriff Buford Pusser, she starred in the cult classic and major box office hit Walking Tall (1973).

[citation needed] In the last few years of her life, she quit acting and worked at a museum in Pittsburgh while receiving treatment for her condition at an outpatient clinic.

[23] Her sister and caretaker, Janet, told the Los Angeles Times: She was very suicidal...  As soon as I arrived, she took an overdose of sleeping pills and was rushed to intensive care.

[1] Earlier that morning, according to the Allegheny County Medical Examiner's Office, she had reportedly called her psychiatrist saying that she felt despondent.