Wow...that's loud. But her comb and wattle look good, not purplish, which would indicate that she's getting oxygen just fine.
Can you give us more info??? Are there any other signs?? How's her energy level? What have you tried so far??
I recently had to have a little pet roo put down due to breathing issues, but his comb/wattles were purplish...the vet suspected (not tested/proven) that he had a fungal infection in his lungs. I told her I'd tried Tylan 50, and she mentioned that it was about the strongest thing out there for chickens, and if that hadn't worked, nothing probably would. I'd had success with Tylan 50 in a milder respiratory case the year before. So have you tried Tylan yet???
Also, What other signs are you seeing that makes you think it might be gapeworm??? Is she shaking her head a lot? Have you looked down her throat and seen something???