This is the revenge for having sex with Kathi's ex-boyfriend. She always told Demi to keep her fingers off him but finally she let herself go. Now she was turned into Kathi's foot slave. Kathi always knew some dirty secrets about her and now it was time to make use of them. Those secrets would bring Demi into great trouble, so it seems that she would rather get used to stay as her living foot and toe sucking bitch for the rest of her life.