C.C.
Hi L.,
Love's advice is right on, and also I wanted to add that her tonsils might be to blame if the dental hygiene alone doesn't resolve the issue. I heard from a friend of mine that she noticed particularly bad breath with her son, and not long after that she had to take him to the doctor for a bad sore throat - turned out that his tonsils were very infected. They had the tonsils removed and both the sore throats and the bad breath went away!
Let us know what happens...