Miss Jellybelly is one of the dolls who belongs to Millie Burtonburger. In Hair Brains Millie warns Coop to "scrub in" to avoid infecting the doll, as she is a patient undergoing a hair transplant procedure after Kat ate most of the dolls' hair.
Her clothing is mostly covered by a white blanket, all that is visible is pink slippers.
The small bits of hair Kat left behind were orange. Millie is replacing it with curled strips of lined white paper. These are later called "Coop's homework" though since one piece is graded D- this indicates she at least is using stuff that has been submitted, which would not interfere as much.