Tricky one this. The answer to a crop bound I do know, but isn't nice, and seldom works.
Try giving her something tempting with vegetable oil in it. This will hopefully help whatever it is IF she has a blockage, go down. If it is a twig, prognosis not good. But, I could be wrong, let's hope I am - can't see why she would eat a twig. She hasn't managed to get hold of a small bone has she (poss picked up after fox raided a bin, or even mouse leftovers)?
My very best wishes.