I agree with Kathy completely, I would NOT stick a needle in there since this does not look like a classic case of ascites. If organs have dropped down in there who knows what you might stick with a needle. In this case, short of veterinary intervention, it's best to just let her be and see...
Almost impossible to say how long her life expectancy might be since we really don't know what is going on in there. I had a hen a few years back with a bulgy rear end similar to that, it was not ascites and the vet suggested some type of hernia where internal organs may have dropped down into...