she may have plaque or tarter deposition between gums and teeth. It can onle cleand by scaling. Go for scaling bad smell can be also due to dry mouth
, gum disease, tooth abcess, tooth decay
and food impaction.
Ask her to use alcohol free mouthwash. Brush regularly two times daily. Floss mouth. And rinse properly after each meal. Try at home, mix few drops of peppermint in lukewarm water and rinse.