N.P.
actually if she is having fruit that is great and fine and not needed to have the veggies as much. It's more important whether the item is a variety of colors then if it's classified as a fruit or veggie. So a red tomato is just as good for you as red watermelon. Both will contain very similar nutritional qualities. Eat a Rainbow should really be your motto. Fruits and Veggies are really ONE foodgroup as there is so much crossover between the two.
That said, if you are still dead set on adding it make sure her lunch is one fruit and one veggie. Tomato sauce on spaghetti counts and is a good place to hide more veggies (you can add a jar of baby food veggies to the sauce). I believe in just keeping offering the veggies and it works great. Celery is hard on little teeth and carrots may be too, try slicing them into slivers.
N.