The only spells I can see of use to Maggie are Increase Charisma and Increase Willpower. Increase Charisma would help her with a few Matrix actions like Crack File and Erase Marks, while Increase Willpower would help her to stay alive much better in the Matrix. They are both fairly low priority, though, but if other team members would benefit from one of those spells as well, then it might be a good choice.