If she were on the ground, the perp could have been leaning down from over her head while scratching her, making the ‘B’ upside down in the pic instead of backwards.
Unless she was out cold, if she was on her chest with the mugger kneeling behind her, and her face was turned to the right and that is why he was carving the B there, then I would expect to see bad road rash, cuts and contusions on the left side of her face and her chin.
Nobody calmly allows their face to be carved up. You don’t know if it is a key or a box cutter at the time, and you would thrash like the devil.