One thing I always notice on every reread is how differently Azriel is written around Gwyn compared to Elain.
Azriel's interactions with Gwyn are almost entirely circumstantial. They happen because she's present during training or because he encounters her while carrying out his duties. Even when he sees her alone, his thought is simply whether it's too late to bank on her. With Elain, however, the pattern is completely different. Azriel consistently chooses to move toward her, seek her out, and initiate the interaction himself.
With Gwyn: He found it already occupied. His shadows had not warned him. It was too late to bank without appearing like he was running. Azriel landed in the ring a few feet from where Gwyn practiced in the chill night, her sword glimmering like ice in the moonlight.
With Elain: Azriel emerged from the sitting room, a glass of wine in hand and wings tucked back to reveal his fine, yet simple black jacket and pants. I felt, more than saw, my sister go still as he approached. [...] in time to see Elain say to Azriel, “Hello.” Az said nothing. No, he just moved toward her.
I found Elain studying it, beautiful in her amethyst-colored gown. I made to move toward her, but someone beat me to it. The shadowsinger was clad in a black jacket and pants similar to Rhysand’s—the fabric immaculately tailored and built to fit his wings. He still wore his Siphons atop either hand, and shadows trailed his footsteps, curling like swirled embers, but there was little sign of the warrior otherwise. Especially as he gently said to my sister, “Happy Solstice.”
Azriel smiled faintly. “Would you like me to show you the garden?”
“Can I set you up in the garden? The herbs you planted are coming in nicely.” “I can help her,” said Azriel, stepping to the table as Elain silently rose. No shadows at his ear, no darkness ringing his fingers as he extended a hand
When Gwyn asks about his powers, Azriel answers politely, but the narration doesn't frame the conversation as something he's particularly invested in. With Elain? He puts his fork down, gives her his undivided attention, and suddenly becomes the Night Court's resident poet.
With Gwyn: She shrugged again, irreverently. Az narrowed his eyes, studying her. “Do you, though?” she pressed. “Sing?” Azriel couldn’t help his soft chuckle. “Yes.” She opened her mouth to ask more, but he didn’t feel like explaining
With Elain: Elain said to Azriel, perhaps the only two civilized ones here, “Can you truly fly?” He set down his fork, blinking. I might have even called him self-conscious. He said, “Yes. Cassian and I hail from a race of faeries called Illyrians. We’re born hearing the song of the wind.” “That’s very beautiful,” she said. “Is it not—frightening, though? To fly so high?” “It is sometimes,” Azriel said.
The rescue scenes are another major contrast. During the Blood Rite, Azriel stays composed and mission-focused despite Gwyn being among those in danger. You'd see Cassian losing his mind over Nesta's safety while Az was way too logical for someone who's supposed "mate" is in danger. But when Elain is taken, his reaction is immediate and deeply personal. That man doesn't care if he dies as long as he go after her.
With Gwyn: “There are plenty of other unspeakable things that could be happening to her,” Cassian said, voice thickening. “To Emerie and Gwyn.” The shadows deepened around Azriel, his Siphons gleaming like cobalt fire. “You—we—trained them well, Cassian. Trust in that. It’s all we can do.”
With Elain: Azriel said, as if in answer to some unspoken debate, “I’m getting her back.” Nesta slid her gaze to the shadowsinger. Azriel’s hazel eyes glowed golden in the shadows. Nesta said, “Then you will die.” Azriel only repeated, rage glazing that stare, “I’m getting her back.”
The aftermath of each rescue also matters. Saving the priestesses is part of Azriel's mission, and once they're safe, he continues pursuing the remaining enemies. When he rescues Elain, despite his own injuries, he refuses to let her go. His attention remains entirely on her, even making sure her chains are removed before anything else.
During the priestesses rescue: Azriel slaughtered all of them within moments. He didn’t hesitate. But I could barely move, and when I tried to get up … He gave me his cloak and wrapped me in it. Morrigan arrived a few minutes later, and then Rhysand appeared, and it became clear some of the soldiers had gotten away with the piece of the Cauldron, so Azriel headed after them. Mor healed me as best she could, then brought me to the library
With Elain: Azriel gently removed the gag from her mouth. “Are you hurt?” She shook her head, devouring the sight of him as if not quite believing it. “You came for me.” The shadowsinger only inclined his head. [...] Azriel still cradling Elain to his chest. He dripped blood behind him the entire time—a trickle compared to the torrent that should be leaking out. [...]One saw Azriel and shouted for a healer to hurry for the spymaster’s tent.[...]Rhys lunged for Azriel, taking Elain from him and gently setting my sister down. Azriel rasped, swaying on his feet, “We need Helion to get these chains off her.”
Then there's the necklace. It wasn't "Gwyn's necklace." It was Elain's necklace. Azriel bought it specifically for Elain. When she returned it, he didn't suddenly decide it belonged to Gwyn. He simply wanted to get rid of a painful reminder, that man doesn't give a single fuck if it goes to another priestess.
With Gwyn: “Look, I . . .” Az searched for the words, his voice becoming quiet. “If there’s another priestess here who might appreciate it, give it to them. But I’m not taking that necklace with me when I leave.”
With Elain: He pulled the small velvet box from the shadows around him. Opened it for her. [...]The golden necklace seemed ordinary—it’s chain unremarkable, the amulet tiny enough that it could be dismissed as an everyday charm. It was a small, flat rose fashioned of stained glass, designed so that when held to the light, the true depth of the colors would become visible. A thing of secret, lovely beauty.[...] He found Elain’s necklace amid the pile.
When you look at these scenes side by side you'd see how Elriel relationship is consistently written with romantic subtext, emotional intimacy, and deliberate choices. GA is written platonically. Note that it is Elain who showed mutual romantic interest with Azriel in canon while there was no mention of Gwyn being attracted to Az. In fact, in the end of ACOSF, she doesn't even know if she will ever leave the library.