A girl who gets jealous of the attention her friend recieves because her friend is prettier and has men give her whatever she wants.
The ugly friend is usually someone who men don't give a damn about. She is usually used for one night, also known as a "bust down" or grenade and men don't even think she's worth a kfc dinner let alone anything else.
The "ugly friend" gets jealous of the prettier girl who gets whatever her heart desires.
This leads to the ugly poor friend lashing out when she realizes what a failure her life is and how she can't attract a decent man like her prettier friend has.
She looks at her life in comparison with her Prettier friend and gets angry.
She realizes she dosen't have the brains, the beauty or the class to ever have anything of worth in life and goes crazy.