I will be saying a prayer for Josi tonight. It was weird, when I was reading your very first post this morning, I thought of her spleen immediately but then I figured that wasn't what was going on or the vets would have already diagnosed it. That is what I lost my Tossie from, we opted to not do the surgery because she was so weak and suffering so we decided to let her leave instead of putting her through surgery when the vet said she probably wouldn't make it, she was almost 13 years old too.
I will ask Tossie to keep an eye on Josi too, she will help her out. Please keep us updated on her, I know she will pull through.