It could be a number of things - simply something in her airway, gapeworms, bronchial inflammation (like occurs with infectious bronchitis), or a respiratory illness.
I would put your ear against her and see if you can pinpoint the origin of the noise: top of throat, mid throat, near the ribs/back.
You can also help her with some VetRx which can help reduce irritation and inflammation in her airway. the 2 ounce bottle of any "species" of VetRx is plenty (rabbit, cat, poultry - or Marshal Pet Peter Rabbit Rx liquid from the pet store). Use it mixed 1/2 and 1/2 with water (a few drops of each, the water very hot - stir in a cup til warm and mixed) on q-tips to swab her nares (nostrils), the roof of her mouth, and put a couple of drops down her beak.
If she hasn't been wormed, I'd consider using fenbendazole paste (SafeGuard for horses - 1 bb sized piece in the beak) in case of gapeworm which actually lodge in the airway and can cause that sort of noise/issue.