The attitude of the nurse may not be proper, especially when

you were so upset. Maybe this is common for busy offices. I had similar situation for my daughter.
After the dentist told me 10 of my daughter's 20 teeth have decayed, I couldn't locate them for more explanation. Maybe this is American way of dealing with Panic. GOD knows! I switched to another dentist anyway.

As far as overdose, I used to give daycare teacher overdose instruction and was found out by her teacher, thanks to that teacher.
Once my daughter's doctor gave her overdose prescription, it is good the doctor found out herself the same afternoon.
Anther time my daughter stole Robitosin and drank more than required. I had to call poison control center and was told that the amount of overdose is not life threatening and to give her water... It is panic for me too...

My suggestion, it is quite common to have overdose. Not each of them are so serious. Just calm down and find out the proper solution.

Since the overdose of your daughter does not actually damage her, it may not be worthwhile to file a claim as you may not win. I know the nurse/doctor hurt your feeling, it is hard to forget, but we may still have to forgive and go on our life in peace...