Theta_Sigma: I wish all the best with your dog. As a fellow owner of a big dog I know they can get into more mischief than smaller dogs that can cause them to get sick. I hope that she gets better and like others have said have her push fluids in case it is some thing she ingested that is making her ill. I know this is a long shot but check her body for any welts/swelling/etc... as my dog got a serious infection due to a bee sting and it getting infected (thankfully the worst thing that happened was some muscle atrophy in the face since the vet said it was potentially life threatening). I am sure you probably checked this but I figured I would suggest it anyway. Good luck, and best wishes to you and your dog. :)
Thank you yes we checkd her for swellings and things that would maybe show from the outside, she only has a skin tag she has had since she was a pup and a fatty lump on her front left leg. It was biopsied a few years ago.
Spinorial: You have my deepest sympathies. Might be that her time's come, though I sincerely hope she gets better. In the end, I just hope that she goes peacefully, whenever that may be.
Agree'd, at her age I dont think it would be fair to have much in the way of surgery or stuff. It comes to what is fairest to the dog, We all want to keep our pets as long as we are able but keeping them when it could be causing them suffering is very unfair.
Older pets dont mix all that well with anesthetics either so that too is a concern