She may be standing in the light, but in order to see her, light has to reflect off of her and reach your eyes, which if you’re on the other side of the darkness bubble, it would have to pass through the darkness bubble to do.
I get that it’s magic, that’s why it’s able to create darkness in a lit area without an opaque source to block the light. The magic itself must somehow be blocking the light, and that’s fine. But there’s no logical way for the person who’s standing in the light to appear less obscured through the darkness than someone in the darkness does, unless the spell bends the light around the bubble. In which case the effect would not be darkness but invisibility.