There's nothing to say you can't have a prose style that's ornate and lyrical. And as you point out others have done so with significant success.
Cormac McCarthy's Blood Meridian has lyricism almost as ornate, and that’s a western; yet somehow he pulled it off brilliantly. Evidently, it can be done successfully.
I think the thing to remember here is that Blood Meridian, a book that had a notoriously difficult time finding traction due to it's ornate prose consistently has a brutal and gritty counterpoint running throughout. It's also on the extreme end of such style, if you've gone further than McCarthy did I'd say that's cause for concern.
So how much is too much? It's too much when the prose obscures what you're trying to say in the text, and that includes the establishment of "ambiance" as you put it. This is something that is easily quantifiable (if at all) and is going to be very subjective based on the readers' tastes. So readers are what you need - as many beta readers as you can, preferably those with similar tastes as to the sort of book you're writing and most importantly those you are able to trust to tell you the truth.
Because the way readers respond is going to be so subjective then context is everything, and what I fear might work against you here is the teen aspect - not because the reader will be expecting a conventional teen story but instead the reputation teens have for being so overwrought and melodramatic.
Let's take a minute to examine the examples you gave:
In her school, she flew amidst a pretty pitying of turtledoves, pulchritudinous girls who to some were genial, greeting them with amities and loves, columbine personas of paradise, au fait but demure, amiable and heavenly, luminous pearls frolicsome and cordial, dancing around them momentarily like uncatchable butterflies, noir fay in couture, mischievous bacchantes flittering away unexpectedly and forever, a swans’ bevy joined by belts of silver taking flight together.
Upon others however they would inflict bitter welts of vituperation, riding down upon them, fell Valkyries brandishing verbal blades of emotional mortification. All including the most steadfast feared their aeries’ approaching dismal shades in mortal anticipation of their shredding talons’ heart crippling humiliation and their ripping beaks of pitiless obloquy.
Such were Kate and her corundum crown of aureate camarilla, a radiant representation of Artemis and her sidereal Pleiades, scintillating desirably but unattainable and inviolable in an eternally atramentous firmament, an unreachable empyrean of joy within an endless void, soaring as a sky parade, dancing as a constellation of sylphs in a moonlit glade.
On a mid-September afternoon when maddened winds enrage the wine-dark seas to flaming waves of roaring foam, quiet Caleb sat alone and still in the senior cafeteria,…
The first and third paragraphs here.. I'm sorry, I have to be blunt, they don't work. At all. It's not lyrical because it doesn't flow, instead it reads like a bit of text that's been sent hurtling through a few dozen Google translate processes while being simultaneously mauled by an automated thesaurus program and a fourteen year-old "poet" with a dark blue streak dyed in their hair who shops exclusively at Hot Topic and complains that their chartered accountant parents just don't understand them.
The second and fourth paragraphs - better. Your overlaying of the high-style elements on the mundane is clearer and the juxtaposition is more effective as a result.
Looking at Kate, he was stunned and saddened more than he had ever been, gazing at her smoky quartz eyes shining darkness as pained as children’s eyes glow joyous and hopeful; her eyes, dark as sadness manifest where light is as a darkness visible, a smoldering grief unnoticed by those who would see only her eyes’ laughing twinkle and miss the breathing embers burning in a gaze infinitely wrathful, helmed embers fierce in preparation for battle, fuming embers emanating from caverns of anguish deep within her soul, caverns descending into fathomless pitch where black memories drift in eternal turmoil.
Personally, I think this is a bit much. You've got six different poetic descriptions of Kate's eyes, and it's excessive. Two of them are of different ember metaphors! There's that 14 year old "misunderstood" poet again. You could very, very easily cut this to one or two at the outside and still hit that ornamental "high" style note you're aiming for without boring the reader to tears.
For comparison here's a snippet of Blood Meridian
On the day following they crossed the malpais afoot, leading the horses upon a lakebed of lava all cracked and reddish black like a pan of dried blood, threading those badlands of dark amber glass like the remnants of some dim legion scrabbling up out of a land accursed, shouldering the little cart over the rifts and ledges, the idiot clinging to the bars and calling hoarsely after the sun like some queer unruly god abducted from a race of degenerates.
One of the reasons the writing in Blood Meridian is described as "dense" is that it packs so much in to the descriptions. Yes everything described in the passage gets a poetic descriptor but each element gets one or two, not six. In just 81 words McCarthy describes multiple actions, the landscape and gives a sense of the weather/climate and the ambiance. You took 99 just on the look in Kate's eyes. You see what I'm getting at? If you have multiple descriptions of something that you think capture it well - spread them out across the book, don't just rattle all six off in one passage.
