Hi,
I just don't know what to say... trying to analyze the situation..
I would give her some antibiotics... seems like its the only answer to a lot of medical problems, but if she has some sort of rip or tear in there, it would cut the risk of infection, or dying from an infection that is.
I think if there was no shell you are supposed to give the chicken access to plenty of oyster shell or anything with lots of calcium- giving her plain (unsweetened) yogurt might be a good idea too. My hens will even drink milk, although I'm pretty sure you are not supposed to make that a daily event. This will provide your chicken with enough calcium to make a shell.
However, if there is a shell inside of her you are going to have to fish around in there, carefully to see if you can get it out. I think if you do a search on this board, or just on google you will find some instructions on how to do that. Having clean rubber glove to do this is the best.
She could be an internal layer, which if she is, there isn't much anyone can do. I just took my hen who has similar issues to the vet and there really is nothing that can be done. I had another hen who had similar issue- and I had the operation done, but she did not survive- the surgery is just too much for their systems to take, and even if they were to pull through (I've heard some do) that the problem could return. Its just way too costly for the chance if you ask me. Sometimes though hens will recover from being sick from this from time to time. I have another hen who was deathly ill for a week last summer, but she recovered and is ok now, although she surely will probably pass from it (internally laying) in the future.
So, sorry to be such a bad news bearer. I do hope that whatever your hen has will pull through. Antibiotics help. Baytril is the best I hear, but its controversial... especially if your hen is still laying because people are not supposed to eat the eggs from a hen that is treated with baytril- it is a health risk for humans. I would do some searches on other options for an antibiotic... maybe someone here can chime in.