Even in the novel, Miria and the next girl are only there and nothing much else.
Story-wise, at least the elf girl makes sense and she adds something, Sherry and Roxanne also had/have active roles only they can fill and played major parts in the story, but Miria and Vesta have nothing going for them except being slightly more exotic than the others, which is very sad...
I shall come back to comment on this when the elf girl is added to the party, which might take more than 5 years at this pace, but it is what it is...