We should know soon enough. If it is indeed a grave illness causing rapid weight loss, it will eventually result in something drastic happening like being unable to move, or collapsing, or losing vision, or something else she cannot simply ignore. At this rate, we are talking weeks not years for such a problem to reveal itself. The other possibility is that if she is on speedy drugs, she just isn't eating her usual calories. That's possible too (although the pizza boxes suggest that her reduction in calories is not very drastic). I am leaning more toward a health issue than a drugs-and-starvation diet here.
