Who is Jeanne from Wasted: A Memoir of Anorexia and Bulimia and what is their importance?

Marya spends a tense vacation in her stepgrandmother's home. Marya indicates that she, her mother and Jeanne all compete against each other to prove who is the most perfect. The three have an unspoken rivalry to see who can eat the least. Jeanne not only buys Marya an outfit that is too small for her, implying Marya is fat; she also insults the girl through an entire lunch together. Jeanne is one of Marya's relatives who sees fat people as being less important than those who are thinner.