Ruptured air sacs occur when one part of the body is bumped or injured. In case it is a leaking or ruptured air sac, here is a video of how it can be deflated with a needle:
Edited to show the right video:
It sounds like a ruptured or leaking air sac, but those don’t normally clear up without being deflated with a needle. Is she puffed up in one certain area, such as her crop?