I think for a growing child the need will persist even with taking Kalydeco. The reason is because the root of the problem with the pancreas will still be present therefore without enzymes it is unlikely that the child would absorb all the minerals and vitamins without the enzyme. Realizing enzymes may in your mind be largely for fat, they are also meant to help a child get "everything" they should out of their food.
The reason people are cutting back on their enzymes is because they are gaining weight on Kalydeco. They are not necessarily absorbing their food better but rather not burning calories as much due to the body not requiring as much energy to run. This is due to lowered heartrate, respiratory rate, and increased lung function.
I hope this helps. She'll still need her enzymes until she is at least 18. Even then I think it is wise to keep using the enzymes and to cut back on food. Otherwise, it's like using cf as a diet if that makes sense. Trust me...most of us have tried this during our teen years (ie. not taking our enzymes to reduce our weight) and the result is bellyaches and possible pancreatitis.