Hello Visit a dentist soon and get them filled. Avoid giving her sweet food or drinks. Maintain her oral hygiene and and use small kids brushes for her that are soft bristled and use a smear layer of tooth paste on brush. Brushing thrice won't work if the teeth are decayed. Wish her good health and happiness Keep me updated with the improvements Regards Dr. Purva Jingar

Once decay has set in ,it cannot Be reversed by simply brushing the teeth. It doesn't work that way . Take your Kid to a dentist or a pedodontist and if She cooperates the tooth can be filled . Once the decay spreads deeper it may require anaesthesia and kids don't like injections . So it is advisable to treat it before it spreads deeper. Simple shallow fillings don't require anaesthesia.