I swear people need to let the old AsuCaga vs AsuMey ship war die already. Between the canonical ring-Haumea stone scene and the (canonical) epilogue card art, plus Athrun's internal monologue during the "obscene delusions" scene in the novelization, and the Escape for Two prequel novella - as an AsuCaga fan, I feel like we won. And it's pretty obvious (to me, at least) that Meyrin's just Athrun's (work) partner for all the spy/covert ops stuff that they do - he's the field agent, she's the voice in his ear piece (and occasional hacker extraordinaire) - and shipper on deck for AsuCaga.
And those extra bonuses for the screening? Those are literally just storyboard line art for a scene from right before the final battle in the movie, because, guess what? Cagalli's still head of state for Orb and she can't exactly just go charging into battle like she did at the Second Battle of Jachin Due (especially since that would kind of ruin the plan Athrun had to get around the whole "Accords can read minds" thing).
So just ... let it go. I'm just going to leave Athrun's internal monologue during the "obscene delusions" scene from volume 2 of the novelization (translation courtesy of ZeonicScanslations) as proof AsuCaga is the intended canonical ship for Athrun:
"Cagalli…" Athrun focused intently on picturing Cagalli. As if clinging to that image. Her spirited golden eyes, her innocent smile that she showed from time to time, the scent of her hair… The supple curves beneath her wet, translucent clothes… The soft sensation of her skin when he embraced her, and the physique beneath… Her strong voice, resolute and clear, urged him to live, to fight with all his might. As he recalled every cherished moment with her, Athrun made a heartfelt vow. To live, to endure—whatever the means, no matter how desperate or unseemly the measures might be. Just as she had once told him.
Because that, right there? That reads like he's deeply in love with Cagalli and has eyes for no one else, not Lacus, not Meer, not Lunamaria, and most definitely not Meyrin. Or Kira for that matter. XD