How is Mama described in the novel, Eighth Moon?

Mama is not an appealing character. She is described as a short, dumpy woman who is suffering from some glandular disease which causes her body to swell up. She also has a terrible temper. She sometimes beats and berates Sansan. She tries to keep Sansan in China by telling her that she belongs to them, that since she and her family raised her, she owes it to them to stay and care for them in their old age.