She's an adult and there isn't much you can do. You could suggest she goes for a complete physical by your family doctor to be sure she doesn't have something wrong with her. If she seems depressed, suffers anxiety attacks or panic attacks then she should also see her doctor as they certainly can help in this area. It's not uncommon for college students to be worn out to a nub because of studying, perhaps working to pay for the tuition or books and that would obviously lead to not eating right. Some students have been know to take uppers and downers to keep them awake to study and the downers to help them sleep. You need to try and talk to this young woman and be sure not to condemn her actions. Just talk and listen! Offer advice and don't demand it of her.