Mrs Montgomery was Victoria’s mother and Brooke's grandmother.
Before the series
Mrs Montgomery had raised her daughter, Victoria Anne Montgomery in Tree Hill with her husband. When Victoria fell in love with a “poor” boy, Mrs Montgomery asked to her daughter to leave him. Eventually Victoria had married with Richard Davis.
Her first name was maybe Penelope, Brooke's middle name or maybe Anne, Victoria's middle name. Although there hasn't been any indication that any of Brooke or Victoria's names came from Mrs Montgomery.