Hello. Make sure your daughter is seeing a doctor that is familiar with CF and or affliated/accredited with/to a CF center.
I was told there are over 1500 mutations, with more being discovered every day. I would give the sweat test another go (at an accredited center).
Did your daughter have a fecal fat/elastase test done yet?
Hang in there and hope you get some answers soon, It is very frustrating not knowing what is wrong with your child.
Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind. ~Dr. Seuss