Whispering Canyon is far from bland, as well. My advice would be to pick something you like and explain to the castmember taking the PS that your mom has dietary restrictions. This will be noted on your PS. Ask for the number you can call to discuss arrangements with the chef-- do this about 48 hours prior to your scheduled meal. When you arrive for your PS and check in, remind the hostess that your mom has dietary restrictions and she will get the chef to personally come out and go over the menu with you, or prepare something to your mom's liking.
Disney is EXCELLENT when it comes to specially prepared meals for those with dietary restrictions. I think your mom will be VERY happy.
Some of my suggestions would be:
Le Cellier at Epcot
Garden Grille at Epcot (this is family style and the food is not at all spicy, character meal)--- check for availability as it will be closed for the preparations of the new attraction in The Land
Crystal Palace-- buffet
Liberty Tree Tavern -- lunch ala carte, dinner family style with characters
50's Prime Time Cafe
Cape May Cafe-- dinner buffet
Chef Mickey's-- character buffet
Kona Cafe
'Ohana--- they can specially prepare the meats without the seasonings, if needed
Narcoosee's
Hope this helps!