She weighs 80 pounds has a bmi of 15.6% and i researched: 22-25% you can conceive. what are chances she will con. and survive after giving birth?

Anorexia: I assume she has an eating disorder. Females at that low weight generally do not ovulate and therefore cannot conceive. I hope that is the case in this situation, as attempting to carry a pregnancy in that debilitated state would be potentially dangerous to both mother and fetus.

Underweight.: Being underweight can affect hormone levels in women, and can affect the ability to conceive. She should gain a bit of healthy weight through healthy eating, assuming there's no medical conditions keeping her underweight. This should really be evaluated, if it hasn't already, with some blood testing.