Hello,
We do advice concious sedation in some cases when the patient is very apprehensive about the treatment. However local anaesthesia is still required if the cavity is very deep. If your daughter is co-operative Nitrous oxide is not needed. About the fillings, would suggest for Composite fillings - tooth coloured fillings. However it is more technique sensitive and requires good isolation of the tooth and no contamination from saliva.
Next Steps
Get radiographs done to check the extent of decay.
Health Tips
Kindly consult a good Pedodontist.