What about if she couldn't actually "Fight" at all?
Hear me out, so, like she has some sort of low-mp tech that runs a routine similar to the fight routine, except it draws on magic power instead of attack power. Like a magic missle. It's non-elemental on its own, but if she has a weapon equipped with an elemental property (whether she uses books or staves or whatever), it takes on that element. Equipping new weapons for Schala, then would increase her magic power and possibly imbue the magic missle with an element. It would cost maybe only one or two mp, but if she's completely drained then she can't attack at all. BUT, in place of the "Fight" command she has something like "Focus," which allows her to use a turn to regenerate some MP. Not fill up, and maybe not even as much as an item would, but enough to magic missile a bunch more and maybe enough to cast a mid-level spell.
Of course she'd still have other spells, too, but I think this would add a fun dynamic to a character who otherwise might seem a little too OP in the maghic department.