Ulcers in the mouth occur due to various reasons. The main reasons however which are most common is due to stress
or any vitamin deficiency
in the body. Going by the history I am inclined to think that they are due to vitamin deficiencies. But before i suggest any remedy we need to pin point the cause. Please get her checked by a good dentist
as after taking a look at the ulcer
one can tell what type of an ulcer it is and what the cause would be. The remedy would then be suggested accordingly.