Am mixing fact with my own theory here so bear with me but as i get from websites she's really the reincarnation of class's pet spider
since D's a g** she may hav made a fake soul as a disguise (that's the Hiiro we know) and put on top her own and when found and classroom blowed up she mixed that soul with spider's
since D's a g** she may hav made a fake soul as a disguise (that's the Hiiro we know) and put on top her own and when found and classroom blowed up she mixed that soul with spider's