Quick thought, might have missed it earlier in the comments. I was wondering if we have a clear excuse as to why Andreth wouldn't marry a man after Aegnor.
Being bitter and heartbroken works, but it would seem odd from the perspective of the other humans (she wasn't with anybody as far as they know, so why would she be heartbroken?). In the live episode, Prof said that the people would consider her an "establishment" who would be above falling in love with others. Though I agree with that, that doesn't stop others from falling for her.
This isn't a groundbreaking suggestion, but could we have a moment in which Andreth turns down a human male (likely because she now recognizes that she wants Aegnor)? I'd envision a scene that starts with said dude leaving Andreth's presence with a sad smile (no dialogue), and another person (woman?) enters in immediately and asks Andreth what that was about, and she can briefly respond. In just a few seconds of screen time, we could establish (1) a reason why human men don't approach Andreth (she refuses them), (2) Andreth's budding awareness of her own love of Aegnor, and maybe (3) a verbal statement of the establishment thing ("yes, I'm surprised he tried, given that you are somewhat above all that").