Well, in this case actually more of a syndrome of threes. A Trinity Syndrome. Don’t have time or inclination to read that link? Well, it’s an interesting article from June 2014 which points out an interesting aspect of how a “strong female character” can end up ultimately unsatisfying in a narrative, because in the end she ends up being sidelined or subverted in favor of the male protagonist. It’s named after Carrie-Anne Moss’s character Trinity from The Matrix, who starts off presented to us as an ultimate badass but it’s all downhill from there as Neo comes into his own. Another example brought up in the article is Wyldstyle from The Lego Movie, again introduced as someone ultra-competent that the buffoonish Emmett is awed by — but she isn’t the Chosen One, he is, and so by the end she’s relegated to a supporting role. When you start thinking about it this is a trope that reoccurs time and time again in fiction. The bumbling nebbish of a man meets some beautiful exotic badass woman who doesn’t have the time of day for him at the beginning, but by the end he’s eclipsed her, saved the day, and almost always wins her love and adoration in the bargain. If that sounds like a fantasy scenario, oh boy howdy is it. Is there anything inherently wrong with that? Well, perhaps not, except that it’s overwhelmingly shown in that particular gender balance. You see, the only sci-fi/fantasy example I’ve really thought of that does the same thing in reverse is the anime series Sailor Moon, where it’s the young girl who’s the scatterbrained incompetent protagonist having to be rescued at first by the mysterious and handsome Tuxedo Mask, until she eventually discovers her true destiny and ends up saving the world (and him). Not coincidentally (as far as I’m concerned), Sailor Moon was created and written by a woman. See, this is one of those things that reinforces my thought that men and women aren’t really alien creatures who can’t possibly understand the way the “other” thinks, because the hero’s journey works for (and speaks to) both genders if given the chance. Also, perhaps unfortunately, the Trinity Syndrome could apply in both cases, but in movies at least we still overwhelmingly see it with the man on the upward arc while the woman stays static or regresses, and at root that’s because most writers are men, writing from a male point of view. I don’t even think it’s consciously sexist in most cases, it’s just much easier to tell a classic hero’s journey tale where everyone else is (or becomes) support. And it still resonates — but yet I fully understand the frustration that can be inherent in seeing your identified representation sidelined, especially if they were introduced looking really cool to start with. So in your own tales when you’ve got your aspiring young lad setting out towards his destiny and he meets that ultra-cool lady, maybe go over those bullet point questions in the article:

1. After being introduced, does your Strong Female Character then fail to do anything fundamentally significant to the outcome of the plot? Anything at all?
2. If she does accomplish something plot-significant, is it primarily getting raped, beaten, or killed to motivate a male hero? Or deciding to have sex with/not have sex with/agreeing to date/deciding to break up with a male hero? Or nagging a male hero into growing up, or nagging him to stop being so heroic? Basically, does she only exist to service the male hero’s needs, development, or motivations?
3. Could your Strong Female Character be seamlessly replaced with a floor lamp with some useful information written on it to help a male hero?
4. Is a fundamental point of your plot that your Strong Female Character is the strongest, smartest, meanest, toughest, or most experienced character in the story—until the protagonist arrives?
5. …or worse, does he enter the story as a bumbling fuck-up, but spend the whole movie rapidly evolving past her, while she stays entirely static, and even cheers him on? Does your Strong Female Character exist primarily so the protagonist can impress her?
6. It’s nice if she’s hyper-cool, but does she only start off that way so a male hero will look even cooler by comparison when he rescues or surpasses her?
7. Is she so strong and capable that she’s never needed rescuing before now, but once the plot kicks into gear, she’s suddenly captured or threatened by the villain, and needs the hero’s intervention? Is breaking down her pride a fundamental part of the story?
8. Does she disappear entirely for the second half/third act of the film, for any reason other than because she’s doing something significant to the plot (besides being a hostage, or dying)?

It’s at least worth keeping under observation.