Disster

A blood relative aka Sister or a close friend or sorority-mate who is a woman who acts as if she likes you until someone else comes around--then she becomes competitive and starts to "Diss" you. Pulling out all of your secrets and hating on you; criticizing everything you say and trying to make you look bad and herself good in front of company.

Ex: Hi, my name is Joanne and this is my sister, Terianne who has a prettier smile than me because she wears a retainer at night for her TMJ."

Joanne just dissed her sister Terianne; Joanne is a "Disster."

Hi, my name is Terianne, and this is my baby 'Disster', Joanne."