The only things I know that can help is to eat more fiber, drink butter milk and eat yogurt, and eat less meat (animal fat). Fast foods and processed foods tend to have more odor than fresh foods. Gut flora produces sulfur containing compounds and that is what you smell. The larger the percentage of vegetables in your diet the less odor there will be.
For most of us it goes straight into the toilet, we wipe quickly and make sure the paper submerged, then we flush. As Martha said, if she is not cleaning properly or leaving fecal matter out of the water it will have more time to create more smell.
Otherwise she may be having gas. It just goes straigh into the air. You might want to ask the doctor to suggest something to reduce the gasiness. The odor of the gas, like the feces, is dependent on the diet and the amount of sulfur containing compounds contained there in.
The things we discuss