During the night my 6 yr old looks like she is chewing/swallowing in her sleep. no teeth grinding, usually 90 mins after falling asleep.concerning?

Backing up: Very common. She learned so much during the day that now she's "backing up" the computer (brain). Also it's a way to manage differential growth. Report this to your child's Dentist, but probably no Rx indicated. And when she turns 7 take her for her 1st Orthodontic screening exam so that a dent-facial growth specialist can follow her development.