Young Girl: Louise is sixteen. Good job on that one.
Superhuman Abilities: Warranted, she doesn't have any.
Fights Evil: The 'fights evil' thing is subjective in that the people they are fighting are considered villainous, or are being manipulated by dark forces.
Protects the Earth: Once again, not checked.
Secret Identity: She goes by the codename 'Zero' when working for the military and the royal family. Nobody knows that she is the Void mage outside of her close circle of friends. Once again, good job in paying attention there.
Plotline involving magic: Most definately check.
Transformation: None here either, no.
So in the end, all I really did serve to prove is that Shana possesses MORE Magical Girl features than Louise does, although they both pretty much define as magical girls all the same.
And it's alright, I wouldn't want to admit to horribly failing in assuming that 'she's not a magical girl because she has a SWORD!!' either. By the way, gaining new abilities because her love interest made her panties moist is VERY magical girl oriented, and less Shounen male.