Ice cream, sour cream on anything she can stand it on, cottage cheese, yogurt, butter on EVERYTHING, Hot chocolate out of protein shake powder (Mark and I recently discovered this, it tastes just like hot chocolate-delicious). As the other mom mentioned, fried chicken, and also peanutbutter, WHEAT bread, brown rice, eggs (cooked any way).
Sprinkle that scandi-cal powder on everything you can before she sees it. It's tasteless and if she doesn't know it's there, she probably won't ever say anything about it.
You said she doesn't like potatoes, does she like french fries? French fries with ranch, french fries with katsup, french fries with sour cream, french fries without anything on them, french fries with cheese... You can also turn the carnation drinks or protein shakes into a milk shake with some vanilla ice cream and chocolate syrup and some scandi-cal powder.
Just a few ideas, good luck. I am a picky eater and I don't have CF, so I feel your pain because I know how much my husband, who DOES have CF struggles to get me to eat when nothing sounds good to me.