simethicone is any brand of over-the-counter infant gas drops. dosing is 1-2cc per hour for three hours, then 1cc every 3-8h if needed. it's incredibly safe for rabbits.
canned pumpkin (plain, not the pie filling kind) is good for keeping the digestive system going - it's tasty and high in fiber.
papaya tablets (some pet stores have them) are good for digestive problems, especially hairballs (caused from grooming themselves during a molt), as is fresh pineapple (or fresh-squeezed juice).
if you need to syringe feed, critical care (can be purchased from vets or online at
http://www.leithpetwerks.com/ ) is great... if you don't have any of that, you can mix water in with pellets and microwave for a couple minutes, then let sit for 10-20 mins while the pellets "fluff". add more water if needed, or if you prefer/worry that she won't eat it, you can mix a little bit of preservative free fruit flavored baby food in with the pellet slurry.
great video on syringe-feeding: [ame]http://www.youtube.com/watch?v=8iGZVYVm5Bg[/ame]
if the bunny stops eating or pooping completely, a vet trip is necessary.