I ditto what Meadow said-- I do almost exactly the same thing. And yes, 7 months preggers I get, I have been that big before and it was crazy how distended my belly was getting.
My suggestion is to try a fully primal, and elimination diet. Eliminate all the grains, dairy, beans, fruit, etc for a month. Then add one item back in at a time, for a week or two and see if there's a reaction. That's really the only way to figure out what foods it might be.
Also, carbonated beverages, any diet drinks (things with aspartame) and alcohol can be huge culprits.
I know it sounds daunting to eliminate all of those, but until she does it will be very difficult to figure out what the problem foods are. Plus you need to eliminate for 30 days to let your guts rest and heal before retrying things. When I did my elimination diet, it took about 3 or 4 days but the bloating was totally and completely gone. Magical!
You can google "elimination diet" for a list of foods to cut out and how to reintegrate them.