Patience, patience, patience...
My 7yo still has nighttime problems; at that age we have actually used an alarm.
Here's a few things to consider/try:
1. It is hereditary. Either you or your husband must have had some sort of problems as a kid. So that means, no punishment. Daytime potty is something they can control, nighttime is harder.
2. Limit drinks before bed.
3. No caffeine or sugars at least an hour before bed.
4. Make sure she is getting to bed at a decent time, and she should still have a nap. When kids are overtired, they sleep too deep to realize they are wetting the bed. If it is a late night for us, then I know someone will wet the bed.
5. I bought waterproof mattress pads, and a sheet protector that feels like a real sheet (you lay it over the sheet) but holds up to 6 cups of liquid. That should cut down on the laundry.
Personally, at that age, I still did pull-ups. I only stopped when they were much older and it was embarrassing to wear a "diaper" to bed. If it gets to be an embarrassment for them, then they are old enough to really work on it.
I tried rewards, but it really wasn't the same as daytime, so the rewards were pointless. I made a huge deal this morning because my boys stayed dry (my girl still wears pull-ups at night). Hang in there; it will happen one day!