Kids usually go to sleep with bottle feeding because of which they develop tooth decay..it called as early childhood caries or nursing bottle caries..
Kids are not cooperative for treatment at this age so need to go for treatment under anesthesia.
Next Steps
take second opinion from pediatric dentist
Health Tips
keep her tooth clean after feeding by small piece of cloth deep in water.
you can use finger brush for cleaning her tooth..
more precaution for early childhood caries you can Google it...