From Shotgun Shuffling
Rosemary Buckingham is the mother of the seven Buckingham sisters. Married to Herb, she is the one who booted Ellie out of the house for being lazy and a bad influence on Pumpkin.
Based on her in-comic presence, and the appearance and insanity references to Herb, Rosemary appears to be the family disciplinarian. Possibly she intimidates her daughters a bit more than she intends.
During the first plot B arc, Rosemary starts to get concerned and then investigating Kat, out of concern that things don't seem quite right. Cognizant of previous fights when concerned about a boyfriend of Ginger's and how far things might go, she attempts a lighter touch. She leaves work early and stakes out her own house and sees Kat there. When she walks in to confront Kat and Pumpkin, she sees her concern wasn't misplaced. Rosemary proceeds to remove the interloper from the premises and make clear that she's no longer welcome.