Gladwell on Foote, indirectly

From Sands Hall's Fair Game? - or Fair Use? on the current Footes' anger at Wallace Stegner's having made extensive use (in his novel Angle of Repose) of Nevada County luminary Mary Hallock Foote's letters and life, while turning her into an adulteress for literary purposes:

...it was not the issue of plagiarism that bothered them: it was the fact that Stegner used so much of Mary's life, and then, by the end of the novel, radically changed who she actually was, and distorted the nature of her relationship with her husband. Many people, not just local friends, recognized the Footes' lives in Stegner's novel, and believed that a skeleton had been exhumed from the family closet.

In his Nov. 22 New Yorker article on plagiarism, Malcolm Gladwell recounts a similar case:

Dorothy Lewis says that one of the things that hurt her most about [the play] 'Frozen' was that Agnetha [the character that was, essentially, her] turns out to have had an affair with her collaborator...Lewis feared that people would think she had..."That’s slander...if everything up to that point is true, then the affair becomes true in the mind...If you are going to take the life of somebody, and make them absolutely identifiable, you don’t create an affair, and you certainly don’t have that as a climax of the play."

In constructing a fictional character by taking artistic license with a non-fictional woman's morals, is the author of 'Frozen' plagiarizing Stegner's plagiarism?

BTW, the Wikipedia page on Angle of Repose is just a stub, and needs you to add to it; the page on Mary Hallock Foote is somewhat more extensive, but could also use your help.