Until 50 years ago the word for a bisexual woman was “lesbian”
I’m not denying that female homosexuality is a natural part of human nature and has always sexisted. There absolutely are and always have been women who are exclusively attracted to only women. The distinction that is relatively recent is the distinction between people who are different levels of attracted to women.
Which is to say, if a woman had sex with other women, the word for her was “lesbian”, regardless of her relationship to men. Until the 1970s.
So for example, in lesbian bars of the 1930s-50s, where butch/femme culture emerged (check out Boots of Leather, Slippers of Gold by Elizabeth Lapovsky Kennedy and Madeline Davis), femmes usually tended to be married to men who financially supported them. While married to their husbands, they went to lesbian bars and had affairs with other women. Bisexual women were part of the lesbian community. When the Daughters of Bilitis, the first lesbian advocacy group in the USA, formed in 1955, a great deal of their work was helping women leave their husbands. Some of them were completely gay and locked in loveless heterosexual marriages with men they were incapable of desiring–some of them were bisexuals who were capable of love and attachment to men, but were actively pursuing relationships with women. To tell which were which would involve delving deeply into their personal thoughts and feelings, which we can only do for a few of them through this much distance and time, because they at the time didn’t think the difference between gay and bisexual women was terribly important.
Or, very rarely, we’d know they were bisexual because it actually entered the historical record. As Genny Beemyn recounts in A Queer Capital: A History of Gay Life in Washington, Part 3, the Mattachine Society’s 1965 protest against homophobic discrimination in federal employment included lesbian Lilli Vincenz walking in the picket line next to self-identified bisexual woman Judith “JD” Kuch.
The split between lesbians and bisexual women as distinct groups dates back to the 1970s, with groups like The Furies Collective, who advocated that women withdraw from male society completely–that women end all working, personal, or casual relationships with men, and with any woman who would not do so also. The Furies are often cited as a landmark in the formation of lesbian feminism and lesbian separatism, but their first newspaper proclaimed, “Lesbianism is not a matter of sexual preference, but rather one of political choice which every woman must make if she is to become woman-identified and thereby end male supremacy.“
That’s where the major division between bisexual and lesbian women came from. It wasn’t a deep interrogation of the nature of lesbian women’s desires; it was appropriation of the word “lesbian” to mean a political choice instead of a sexual orientation. It comes from the sense that the choice to work with, be friends with, or sleep with men is a choice to be complicit in women’s oppression. From this comes the idea that bisexual women are less trustworthy, less capable of truly loving other women, and less deserving of a place in lesbian society.
This attitude about bisexual women shows in personal stories of the 1970s. For example, lesbian feminist Robin Tyler recalls an argument at the 1973 West Coast Lesbian Feminist Conference, where some members wanted to remove invited musician Beth Elliot from the stage because she was a trans woman: “When Robin Morgan came out against Beth, I said to her, look, you’re bisexual and you’re up here determining who should belong to this movement and who shouldn’t?“
Then in 1979, the lesbian sex manual Sapphistry by Pat Califia was being prepared for publication when its author came out as bisexual in an article for The Advocate. Its publisher immediately threatened to cancel publication of the book–a book about how women could have sex with women–because “we do not publish books by bisexual women!” (She later relented, and the book was published in 1980.)
History makes it very clear that it took active work to push bisexual women out of the lesbian community, and it hasn’t entirely stuck over the years–after all, most towns or cities don’t have a large enough LGBTQ+ population to have both a lesbian separatist potluck and a queer-friendly WLW sapphic potluck. A woman looking to date other women goes to lesbian events because that’s all there are in most places. We didn’t fight for “gay and sapphic marriage”, despite the number of bisexual women who wanted to marry other women; politically, bi women in relationships with women have always been grouped under “lesbian”, and there has been almost no push, especially not from lesbians, to popularize “sapphic” as the default descriptor for women attracted to women but with unknown sexual histories and/or personal desires.