So I have a companion who the player can ask via dialogue to cast various healing spells or buffs on the player. However, I am worried she will cast these (the healing spells at least) on hostiles too.

Apparently the "cast" command does not require that the spell in question be in the companion's spell list at all to force them to cast the spell at the given target. Is there any disadvantage to removing all such spells from companion's spell list to prevent potential healing hostiles, and just relying on "cast" and "modcurrentmagicka" commands in dialogue to get her to cast them on the player?