You have a female character: she is strong, has awesome combat skills, she has perfect agency, makes her own decisions, she is lacking in spunky agency, she is sexual without shame. She is a leader, she is capable, she doesn’t need rescuing and she doesn’t spend all her time being victimised and kidnapped. She takes no shit and she won’t be controlled - yet without being rebellious for the sake of it. So far so good.
Then she meets another female character. She is also strong and has a lot of agency and all those wonderful things we love to see. And that’s it, it’s time for a scene from Highlander. I expect them both to draw their swords and fight to the death - because there can only ever be one!
Time and again we see this. If we do get a strong (or supposedly strong) female protagonist, she cannot have any female peers. She can have male equals, men who are as capable and demanding and powerful as she is - but never another female peer. Often this manifests by simply not having any women around the main character at all - or not for any length of time. Women, when they appear, are reduced to bit characters, villains or victims. We see one woman surrounded by dozens and dozens of men.
We see lots of series like this with female characters surrounded by men and, if there are other women there, they have no close relationships with them - Patricia Brigg’s Mercy Thomas Series, Kristen Painter’s House of Comarré, Pip Ballentine and Tee Morris’s A Ministry of Peculiar Occurrences, Karen Chance’s Cassandra Palmer Series, Jocelynn Drake’s Dark Days Series, Jeaniene Frost’s Night Huntress Series, MLN Hannover’s Black Sun’s Daughter Series, Tanya Huff’s Victoria Nelson Series - over and over we’re seeing the same pattern, the same large group of men with one lonely woman.
If we do actually get other female characters, they’re often secondary or lesser to the main character - weaker, less capable, in need of saving or in some way clearly labelled as not being the protagonist’s equal.
If there is another strong female character then, predictably, they will instantly hate and/or be hated by the protagonist. She is never a peer, an equal, someone due respect - she is competition, a threat, a challenge.
One example of this would be the relationship between Kiera and Betty on Continuum. From the moment Betty meets the protagonist Kiera, she views her as a threat and is decidedly unpleasant towards her. Kiera is there to partner with Carlos to track down Liber8 but because Betty used to date Carlos, Kiera, of course, must be threat. Whoever heard of men and women working in a professional capacity together. Oh the horror.
In the Richelle Mead’s Succubus series, Georgina is largely surrounded by men. Much of the story revolves around her relationship with author Seth. When she does finally get a female friend in Maddie Sato the friendship quickly dissolves when she starts to date Seth. This is certainly set up as a love triangle in which true love always wins the day; however, this means that once again, we have a strong female protagonist with absolutely no female friends in the end. Maddie’s lost is justified because Georgina gains her one true love forever. The only other female character we see (she has many male friends) is a new, inept Succubus, who she has to mentor - instantly placed in an inferior position to Georgina.
In Blood Ties, Vicki Nelson gets on well with Coreen, her secretary - her assistant, her employee who she has rescued; in other words, in no way a challenge to Vicki or at her level. But the other strong female characters? Crowley, the police chief, hates Vicki despite Vicki once working with her. And there’s Kate, the police detective who clashes with Vicki immensely (including added jealousy over Celluci - because strong women must fight over men). Even when the clashes are justified in the story, it’s still telling that they have been written in a way that instantly creates conflict.
Sookie Stackhouse in both True Blood and especially in the Sookie Stackhouse Books has a truly fraught relationship with women. On the TV show the way she treats Tara is beyond shoddy and as for the other women in her life like... like... uh... does she even talk to Arlene any more? Or Debbie, wait, hated her and killed her. Or there’s.... Marnee, oh wait enemy and dead. Pam hates Sookie, for good reason, and expresses so repeatedly. In the books it’s no better - Arlene starts as a friend but quickly jumps on the train of Sookie hate. Tara is repeatedly victimised before drifting away and Sookie’s constant pastime is judging and hating other women - she can’t even think of her grandmother any more without constantly dwelling on her infidelity, because she spent far too many books actually admiring a woman and we have to take that back.
We even get situations like Vicki Pettersson’s Zodiac Series where there are women around - but she has no close relationships with any of them (and, of course, one of them completely and utterly hates her) - the women are there, but in the background; the close relationships are always with men.
We’ve already mentioned Laurell K Hamilton’s Anita Blake Series.
Together, this is an extremely unpleasant trope that presents strong women as inherent enemies and that the natural allies and peers of strong women are men. When a woman is strong and capable, she is presented as standing above other women - the only people worthy of being her equals, her peers are men. She is not an exceptional woman, she is a woman who is exceptional despite being a woman. It is almost implied that she has reached honorary man status - a standard other women clearly do not meet. Not only that, but her pedestal becomes a precious state she has to protect from other women: because it’s a pinnacle only a few women are allowed to occupy.