Terry, try a few nights of giving her truly 'free' foods - like string cheese or hard boiled egg. (I know, not so fun as a bedtime snack!) and then check her every 2-3 hours that night. She might require a bump in her basal insulin. Our son naturally spikes right after he falls asleep - our ped endo said they see this a lot in kids, that they fall asleep so hard that they get a rush of hormones working quickly after they fall asleep and need more basal insulin then. He is on a pump now and his basal rate for 8pm- 2am is over 2x what is during most of the rest of the day.
I'd talk with your clinic about ways to manage it, she might just need a little boost of insulin at bedtime no matter what kind of snack she has. And if that's the case, she might as well have one that she likes and just take the extra insulin for it.