How did Mary learn to cope with her mother's mental instability, particularly after Charlie's breakdown after inheriting a large sum of money from Grandma Moore?

Mary adopted many different coping methods during her mother's mental breakdown. First, she tried to simply ignore her mother. Then, she began constricting her stomach, imagining her insides turning into knots. Finally, during the climax where her mother threatened her with a knife, Mary began to see the world in cartoon rather than reality. She saw her mother and sister as stick figures, which made the violence around her suddenly palatable.