D.M.
My son is very picky too. He will only eat peanut butter (no jelly) sandwiches. So I buy only the health snacks he likes, eg. his favorite fruits, pretzels, chocolate milk, fruit juices he likes. I let him have his peanut butter sandwich everyday and then he has to pick snacks and a drink cover the food groups.
Enjoy controling her lunch now because once they start high school they can buy just about anything for lunch. (Cookies, chips, etc.)