Turn her upside down and massage out the liquid in the crop. You have to do this quite quickly so she doesn't gag and inhale the liquid into her lungs.
Keep her warm and quiet and withhold food. Put apple cider vinegar into her water. Try to put a bit of live yoghurt into her beak, it's important she swallows it, not inhales it. You're trying to acidify the crop contents so that the fungi that is fermenting food in there can't survive.
Do this for two days at most.
Then you need to start feeding her again, scrambled egg is best. Chick crumbs too if you can get them at this time of year.
You may need to keep on with the ACV in the water, live yoghurt and massaging the crop to empty it of excess liquid for two or three weeks, but they can recover.