The Un-named younger sister of an inter-dimentional demon, called Pinface. Like her older brother, she has purple skin, wears a long dark purple robe, but the most distinct physical feature that she shares with her brother, (and possibly with her whole family,) is that she has bowling pins growing out of her skull.
When she and her older brother were kids, they used to live across the street from a younger Grim, in The Underworld, but when her and Pinface's father got a new job in The Netherworld, her family had to relocate there.
Some years later she and Grim met with each other at the Netherworld mall and hung out. They dated briefly, but Grim broke it off on account that everytime they tried to make out, the bowling pins that stick out of her skull kept poking Grim in his eye-sockets--although, according to her brother, she never understood herself why Grim broke up with her.
She still remains stuck on Grim, however, as she is seen being affectionate with Grim when he was stuck with her and Pinface in The Netherworld at the end of the episode. Grim was protesting her advances, as her brother watched angry.