If it feels like a water balloon than there will usually be fluid building up in the lower part of the abdominal cavity. The eggs from internal laying or lash egg mass with salpingitis float or sit higher in the body, so that fluid in the bottom can be drained by inserting a short but large gauge (16 or ideally 14) needle and drawing it off into a syringe. Usually multiple syringe fulls will be removed as there can be more than a pint of fluid build up. That will make her instantly more comfortable but does come with risks of introducing an infection or shock due to drop in body pressure. You need to be aware that the underlying cause will prove terminal anyway, so you are not really risking much for instant improved quality of life. I saw a very good instructional video about it the other day that someone posted.... the best video I have seen on the subject.... I will see if I can find it again and link it. I am sure watching it will give you a better understanding.
