Sharlee,
I hope all is well with you and your daughter. Did your daughters dentist take an x-ray?.. and if so did it show signs of infection?
It is not uncommon for children of your daughters age to develop large nodes in response to a dental abcess of a primary tooth. In children, I have found in my experience, that nodes can become alarmingly large. I become concerned when theses nodes are hard and fixated (immobile). Enlarged, mobile nodes by them self are an indicator that your daughter's immune system is fighting something and working properly. If they are hard and non mobile that presents the possibility that something is not normal.
I know as a parent it is hard to relax when something is affecting your child, but don't get too wound up over node size.
If it is determined that your daughter should have a lymph node biopsy you can rest assured that the surgeon, Dentists don't perform these, that your daughter would be sedated or anesthetized so that it was not a painful procedure. Oral surgeons are qualified and in some areas do perform this procedure. I would assure anyone who is in doubt of an Oral Surgeon doing this that the ones who do are fully capable of performing the procedure. I am only aware of one who does in my region and he usually works in the OR with an ENT.

Shar, let me know how everything goes. Chances are that the cavity has involved the nerve of the tooth and that is the reason for the nodes. You can never be too cautious though, go with your gut.
I'm praying for you and your daughter.

Mike