When I suspect one of my rabbits has belly problems, the first thing I do is make them move, or give them gentle belly massages to get things going. Usually I put the whole rabbit on my leg facing me, balancing my foot on the palm, and rocking it. It becomes obvious pretty quick if it feels good to the rabbit. Repeat that hourly for 5-10 minutes.
Offer everything she is used to, you can also offer safe greens like narrowleaf plantain or leafs from apple trees, roses, bramble, even if she's not used to greens.
You can syringe feed her some water, and mix some Simethicone (Infant gas relief drops) in, about 20mg min. every 3-4 hours.
I would see if there's a way to see a vet asap too, even if it's not your usual one.