Just to give you a full range of opinions on this, I would separate her for the reason given above in that she needs a restricted diet (liquid only) and poop monitoring, but also bring her into the warmth of the house and maybe also give her a heat source. The reason being that she has already essentially been living off her body condition because not enough food is passing through her system and if she is now bone thin she has no body reserves left to keep her warm, so providing a heat source will safe her from burning off more energy than she can afford.
How old is she and what breed? Crop problems can be as a result of a problem with the crop and it's contents or due to a blockage lower down the digestive tract causing her to get backed up. Reproductive problems suffered by older hens commonly cause the latter. A bit of history about the bird and your ownership of her and management might help. Does she have access to long grass or fibrous material... hay/straw alfalfa? Do you provide grit? The more information you can give us the better chance we have of figuring out why she is having this problem and the best way to proceed.
How old is she and what breed? Crop problems can be as a result of a problem with the crop and it's contents or due to a blockage lower down the digestive tract causing her to get backed up. Reproductive problems suffered by older hens commonly cause the latter. A bit of history about the bird and your ownership of her and management might help. Does she have access to long grass or fibrous material... hay/straw alfalfa? Do you provide grit? The more information you can give us the better chance we have of figuring out why she is having this problem and the best way to proceed.