Abby is the five-year-old niece of Glenn Quagmire. She suffers from brain cancer. In "Road to the North Pole", her uncle takes her to sit on Santa Claus's lap at the mall so she can tell him what she wants for Christmas. Her uncle's enemy, Brian Griffin, tries to make amends with Uncle Glenn by being nice to her. However, he mistakes her for a nephew and scares her into thinking she's dying.

When Brian and Stewie get home, Lois gets a call from Glenn saying that Abby's cancer has returned and that she is in the Intensive Care unit at the hospital.

Abby is voiced by Karley Scott Collins.