Hmmm...well, I'm definitely not a doctor, so don't take my thoughts as fact

My first thought, is if it's gas, why only at night? Is it possible that it's night terrors? Is she unsettled/fussy during the day too?
Have you ever tried probiotics? The research done was with colicky infants, but since they're natural, I would give them a try to see if they help at all. They're more for helping digestion, but I would imagine it could help with gas too...