4 yo girl'st&a were removed a year ago. but she still snores, night terrors, grinds teeth, gags in sleep. what could cause this?(ent appt next month)

Many causes: Despite tonsillectomy, many children still have sleep disruption as you have described. Potential causes include acid reflux, central apnea, excessive weight, anxiety and a variety of other sleep disorders. Your ENT should be able to help you sort this out. Best wishes.

Sleep evaluation: concider seeing a pediatric sleep specialist to evaluate her sleep. They will work with the ENT and her primary care doctor.