call a paramedic or hospital and have them explain it to her. my old roommates infant died from this exact thing. you dont ever ever ever want to see a 3 month old turn blue. what do you have to lose and what do you have to gain from laying them on their backs and not their bellies. i know the risk, because ive seen it first hand. whatever you have to do to get it through her thick skull. call the same people that you would have to call if the worst were to happen. they'll set her straight.