I too had ( have) the same issues,. 50% of it is to do with your enzymes doses and how food is affecting you, and the other 50% is antibiotic use trashing the flora in our gut.
I stay away from heavy meats, high fat foods, no fast food, only little pizza/ only a little at a time! But Milk, dairy, wheat, gluten, bread, doesn't upset me, its just anything with fat. I have found being a vegetarian helps a WHOLE LOT, I don't eat beef, pork, fish, but I occasionally eat little turkey or chicken, because I have to keep my weight up,
I also eat
ALOT of fat free yogurt, chobani , greek, yogurt drinks, and take probiotics supplement daily, which is
tremendous benefit, and I have virtually zero CF -related farting. (FART)
As for your mother-law, I can't blame her for proclaiming you and CFer's in general are a living sewer (NOSEPICK) yes even though you 'can't help it' per say, you can control it alot better.
Try pass it away from her or somewhere in the bathroom, and have a can of Lysol at the ready, until you figure things out, or if you want drive her insane, do nothing and maybe she'll leave. (FART)