Mill (the younger one) just wouldn't make sense to me. her eidolons are good but suffer from 1 cooldown. meanwhile in rance 8 she has 50 uses for that skill before retiring. her "wrong stats" also confuses me a lot. why is she not a mage with such high int stat? it's like she's stuck to a job that doesn't suit her at all. finally does she have some backstory with the eidolons? I assume she doesn't first appear in rance 3 so maybe I'm missing some huge backstory with her.
The 1 turn cooldown problem isn't unique to her, like all magic attacks suffer cooldown, Sill's "Fire Arrow" or Aten's 1st skill all are nearly identical being a 1 cooldown magic attack with the same multipliers.
I think it's a shame her stats are not well rounded instead of being completely trash in melee and merely decent in magic, so that she could pick the one that is best in that situation, like physical when facing a Hanny, but since her physical is so trash as it stands, she basically tickles them if she isn't using her magic stat.
She first appeared in Rance 2 if you want the backstory stuff.