A few days ago? How long has this been happening? You might need to take her to the vet. If it's a blockage she may need surgery. Kinda like rabbits and hairballs....
Ooooh, poor thing...that crop is huge! The problem is, this could be anything from sour crop to an inherited muscle disease that affects the tissues surrounding the crop. It could even be a bit of something she swallowed that is now causing an abscess. Without an xray and proper veterinary...