Given the extreme control over Alexandra’s mental state and senses Lumina has with the brain implant, she regularly projects her own appearance into Alexandra’s perception through the neural implant. For Alexandra, it’s as if Lumina was truly physically there in the world, although the entire thing is more like an illusion, as only Alexandra perceives it that way. When Lumina’s projection is present, the two talk audibly and through their mental connection at the same time.
It is important, that this projection is absolute and directly done through the brain implant. This ensures that every sensation, from sight, touch, sound, and even smell, is properly manipulated for Alexandra to feel as if Lumina were present in her reality.
But at the same time, it truly is just an illusion and Lumina’s projection can’t actually directly interact with reality. The only exception is if it’s with Alexandra’s body, as then the reactions are also just simulated by the physics engine and brain implant.