J.S.
I work in a dentists office. A root canal on a baby tooth is not the same thing as a root canal on an adult tooth. It's much easier and much quicker. They will numb her up so she won't feel anything. After they will place some medicine in her tooth so she'll be comfortable. Certainly get a second opinion if that will make you feel better, but if it is recommened, you definitely want to get the treatment done. If the infection spreads she may end up losing that tooth. Like they said, she will have that tooth until she is 11-12 so if the tooth is gone, her other teeth may adjust leaving not enough room for the permanent tooth to come through...leading to other problems, possible orthodontics. Good luck~