Oh, nice, looks like I managed to knock out one of her teeth. I then stepped across the arena as she fired a shadowy projectile at my shadow, while simultaneously disappearing into her own shadow as I evaded her attack.
I then made my way over to the middle of the arena while keeping an eye out around, stepping onto the spot where the shadows of the pillars around the arena intersected, my own shadow overlapping within that spot.
If she emerges in front of me or to the sides, I'll be able to spot her and react accordingly. And if I don't see her, that means she's behind me, nice and simple.
I noticed something about her Magic during her previous fights, right as she starts to emerge from a shadow, that shadow, and any other shadows connected to it, darkens slightly.