i don't know the details of her fracture (type severity which bone etc. ) but assuming she does not have any swelling inside the cast there should be no reason she cannot fly. because i lack these details you will need to call the doctor who put on that cast. the real challenges may be after you arrive in the bahamas. the big issue will be swimming. if you have a waterproof cast it may be fine as long as you rinse it out. over and over again. from any salt water exposure. you can buy a waterproof cast cover assuming you can find one that is the right size so she can still enjoy the vacation. no cast is "sand proof" so that is going to be an issue as well.
my 5 year old broke her arm saturday night and i'm flying from ny to the bahamas tomorrow. can she fly with a cast on? . or does the cast have to be removed for the duration of the flight (2. 5 hrs)