Truman Capote's quote, "That's not writing, that's typing," was in reference to Jack Kerouac, not Jacqueline Susann.
In a scene set just prior to the publication of "Valley of the Dolls" in early 1966, a publishing house employee is seen wearing a fringed vest that would not become popular for several years. Also the soundtrack plays the Deep Purple version of "Hush" which was recorded in 1968.
When Irving is reading aloud from the last page of the Valley of the Dolls manuscript, what he is saying is totally different from text seen in a close-up of the last page, an actual transcript of the book's real ending.
Jacqueline Susann watches people waiting in line at the Radio City Music Hall to see Once Is Not Enough (1975). Susann died the year before this movie was released.
When Jackie appears on "The Tonight Show" in 1966, the set and Johnny Carson's appearance are not from one of his mid-1960s broadcasts from New York, but instead from some years later, when the show moved to Los Angeles in the early 1970s.