This is a really hard situation to answer, just because we don't have all the variables. We can't see the x-rays, we can't judge the vet's experience, we don't know what meds were given and we couldn't physically examine her, making it very hard to know how to answer, let alone recommend what you should ask be refunded, if anything. A lot of times, when a bunny or other similar animal shows signs of gas, it isn't until it's been going on for a long time and by then secondary complications set in, making treatment difficult.
I will tell you that if a blockage or GI obstruction is suspect at all, metoclopramide (Reglan) and cisapride (Propulsid) are contra-indicated, because they can cause intestinal rupture.
IMO, if the vet didn't rule this out and used these meds, something may have been going on that wasn't thought about and the meds could have potentially caused a problem (however, we don't know the time frame either - I'd think it would take longer than 3 hours for an intestinal rupture to cause death). BUT, if this was ruled out or not suspected, you asked for a consultation, the x-rays were needed to diagnose a problem, and the meds were needed to treat a problem, meaning they were legitimate charges.
As I said, it's a tough situation. If nothing else, I'd discuss it with your vet for sure, ask why they used what they used and on what grounds, etc. I'm very sorry for your loss.