i remember being that age and having this phobia, i am now 30. its great that youve realized and acknowledge that this is a serious problem as it could lead to depression, ocd, anxiety disorder , or eating disorders. but you dont need to go through all that. until you can see a profesional i think you should try talking to her and letting her know that you understand this fear and are not trying to minimize it. because this fear is very real to us. im sure you know that what she needs most right now is your support. good luck .