Donna's father, Vincent, was knocked over by a woman at the mall because he grabbed her butt and fell into a perfume stand, causing a hand laceration that needed stitches. He also had pain in his abdomen, so Meredith ordered a CT and sent Jackson to suture the wound. When Meredith observed a gripping reflex that is usually only present in infants while attempting to discharge him, she ordered a CT and a neuro consult. The CT revealed a tumor, but Dr. Clemens, their neuro consult, said it was too far along to operate. Even when Derek offered to talk him through how to remove it, he decided instead to send Vincent out to another hospital.
Donna was the only person in her family who stood with her father after he began grabbing women inappropriately. When it was discovered that he had a brain tumor, which was causing his behavior, she was shocked.