Peanut butter is often good for fussy kids, my younger sister went through phases of not eating her sandwiches so when that happened we both were put back on the peanut butter which she would eat. As long as there is plenty of protein and fruit in your daughters diet you probably shouldn't worry.
When I was 11 I was considered old enough to make my own packed lunch, we had all the bits an pieces in the cupbord and all I had to do was put them in my bag! Admittidly I didn't always eat them at lunchtime but still.