Who is Reetha from The Murderer's Daughters and what is their importance?

Reetha lives at the orphanage where Merry and Lulu live. She is the bully, who cuts off Merry's ponytail, as well as the shirt she was given by her grandmother. Reetha makes life difficult for Merry, and her behavior causes Lulu to find an alternate living situation before Merry comes to real harm.