"Nothing tastes as good as thin feels" is a common mantra on anorexic communities. A few other things you mentioned from her old posts indicates an unhealthy relationship with food including the urgency. When the motivation is right, there is much less fight internally I think. Anorexics have a huge internal battle when they strive not to eat and it is often motivated by self loathing and need for control.
Whatever the situation here, when the motivations become grounded in something deeper and calming (like a healthy interest in nutritious food and good health) then fasting will not be so difficult. Eh, my 2 cents anyway.