Alm and Celica's dynamic had potential. If they were truly meant to symbolize Duma and Mila, Alm should have been a shade darker, more battle-thirsty, like in Awakening—a true representative of Rigelian royalty; instead, Alm didn't want to fight either, so Celica's pacifistic altruism had little contrast, and her character's purpose was undercut.
I enjoyed their confrontation at the end of Chapter 2. It did feel realistic. Not because of their genders—what a frustrating stereotype for him to evoke—but because Alm was high on his victory over the nobility, and off-handedly voiced his resentment, which was an unwitting slap in Celica's face due to her secret heritage. He didn't mean to hurt her, but that doesn't mean her feelings were irrational, since her childhood best friend had just voiced derision toward what she was, after reaffirming his military ambitions that she had envisioned leading to his demise (and that threaten her royal claim).
Then, of course, they threw her character's ability to reason off a cliff in the back-half. Her damseling for Conrad ex machina didn't help, either. She obviously should have retained her agency and mental faculties in a better imagining of Echoes' plot, and her and Alm's groups confronted Jedah and Duma as equals, rather than Alm as savior.