I decided, out of sheer boredom, to level grind Alisa and Basil before facing Malice, just to see what would happen if I defeated her. As of this topic's creation, they're both at Level 27.
I doubt it's actually possible to defeat Malice at the very beginning of the game, given how much health she has and how little damage Alisa and Basil do to her, but I was just wondering if there was a special failsafe scenario in the unlikely event that Malice is defeated at the beginning of the game.