This is a situation where she needs to take a step backward in order to move forward. The worst thing she could do is lower her net caloric intake again via diet or lots of exercise, as that will just reinforce "starvation mode" to her body.
I would suggest she starts by eating natural whole foods to fill for a few weeks. Its probably best to avoid tracking calories or scale weight during this time, because of the potential psychological impact. She isn't likely to gain any "bad" weight with these foods and it sounds like her body could really use the nutrients.
Progress can be measured by trying to determine her basal temperature; it's probably quite low now (almost nobody on the planet actually has a 98.6 deg. temperature). I'd suggest measuring this first thing each morning. As she eats well, per above, her temperature should slowly rise. Somewhere in the upper 97's might be a good target to shoot for, but some significant gain is a good sign that her body's state is improving.
Regarding exercise, the Body By Science workout might be a good choice, as the workouts are infrequent and burn few calories, while still encouraging muscular growth and cellular cardiovascular efficiency.