My sister came.over last night with her kids (19 months and 9). Her younger girl was hungry and so was my 3 yr old so I offered snack time. My sister got really upset with what I had to offer she said she was fine with them eating apple slices but she felt wheat chex were not a snack. I thought perhaps she was concerned about carbs as our dad has blood sugar problems. No this was not the issue. Where were my cookies, fruit snacks, and crackers? I said wheat chex were a lot like wheat crackers. At this point she said she didn't understand why I fed my son that way and she felt sorry for him.
I don't think that makes her ignorant to nutrition, she probably know what you are giving your child is healthier, but rather she just doesn't make it a priority. It's tough to change children's eating habits sometimes, perhaps this is why her children get less nutritional snacks. I'm more like you though. DD is a pretty healthy eater and I think much of it is just because that is what she has been around. She'd choose a banana over a cookie most days.