She lived with my sister for a couple of years and did the same thing and it drove her crazy. I love my mother so much but it is really starting to affect me. I need the positives right now in my life and I feel like someone has kicked me and I am full time care giver for her. Thanks!
If that doesn't/won't work, then firmly interrupt her immediately within the first words out of her mouth, change the subject to re-direct her focus off of her bowels and food, and keep ignoring it.