C.M.
Hi, I'm a dental hygienist in a family practice and we do have several children come in with cavities. Sometimes they are just unavoidable. If it is a cavity, she will need to have it filled because if it is on her back tooth she will have that tooth until she is about 11 or 12. Hopefully, you are going to a pediatric dentist because if she does need a filling done they are much better equipped to handle a small child than even a family practice. Good luck!