why does linda knock the flowers to the floor?

Happy and Biff return home to find their mother there. Happy gives her flowers, and tells Linda that he and Biff met two girls. Linda knocks the flowers to the floor at Biff's feet. She asks whether they care if their father lives or dies. She says that they wouldn't even abandon a stranger at the restaurant as they did their father. Linda asks Happy if he had to go to his "lousy rotten whores" tonight, but Happy insists that all they did was follow Biff around trying to cheer him up. Linda throws them out, calling them a pair of animals.