I hate to disagree with everybody but I don't think 1200 cal is too low for someone her size. I'd look hard at food quality and training. Is she doing alot of cardio? I'd say of she's trying to gain muscle then drop that or reduce it to a couple days of easy cardio 20-30 minutes tops, I'd prefer to drop it entirely. We definately need more info though. Compound movements, lots of rest, sleep is huge, possibly the most important factor. Red meat, fish, quality fats. If you can up the calories, fine, but you can only stuff so much food in such a small body. Overstressing her system with a shit ton of food won't help.