This is a pretty good article going into detail about Hepburn’s identity as well as how the era sort of impacted her experience. She described herself later in life as “the missing link between genders” and even as a child, had a secret name for herself which she preferred to be called among friends (Jimmy) and the information she gave about her childhood like not getting why everyone seemed to treat her like a girl, not wanting anything to do with feminine things, having a secret name, at the very least resonates with gnc and butch women, trans men and nonbinary people.
We have no way of knowing what she really was, and we cant really ascribe an identity to her, but she had relationships with men and women and wanted pretty much nothing to do with womanhood in her private life. Being non straight and/or not cis in Hollywood, especially back then, was such a minefield to navigate, and there was virtually no language to express yourself if your identity was anything other than gay or straight cis person, and even the term ‘lesbian’ wasnt used as often as youd think.