Paired with her husband, they sort of cancel each other out and he's a more prominent character...
Where literally every scene he's involved in and slightly more than half of his lines have something to do with Amanda.
In which case you'd be hard pressed to prevent her from being written out of the movie altogether, since there's no real reason for "The Captain's Yeoman" to have any meaningful lines that couldn't be attributed to Spock, Uhura, Carol or Bones.
I'd still be happy if she appeared.
No you wouldn't. Especially since you wouldn't notice that she DID appear
if she didn't have any lines, especially so if she died three minutes after her first silent appearance.
Nonsense. There are quite a few supporting male cast members. Just use the women instead. Simples.
And they did. Very prominently, in fact.
Lol - I'm willing to bet that they had more than enough actresses auditioning, just not that many role for them to fill.
You know better than that. "Extras" are cast based on a broad set of qualifications, but gender isn't one of them. If they had majority females auditioning for those roles, there'd be a majority of females in the background of the crew.
You're implying that female actresses have a tendency to gravitate towards science fiction/action films despite the fact that you have to know, on some level, that this is not the case. If women are under-represented in this regard, it's primarily because of the lack of desire to BE represented.