D was in the classroom, the main reason why the classroom was targeted by the magic in the first place was because of D. So who did D reincarnate as? She didn't, you think two mortals could do any damage to the dark god of evil? There was also another "soul" that got reincarnated in the classroom. A spider in the corner of the classroom. D just implanted her memory on her before reincarnating. So to answer your question, a literal answer is 'making her web', the other answer is 'running the underworld'.