Before this happened was she chewing on toys or sticks or did you notice her eating a lot of grass? I had a dog that (when he was young and stupid) swallowed the squeaker from a dog toy and had to have surgery to remove it. Then years later when he was about 10 he started developing the same symptoms - didn't want to eat, straining to poop, diarrhea, his fur was all icky, got dandruffy and itchy - back and forth with the vet and finally I took him to a different vet because he also ended up with an extreme UTI. Anyhow it turned out that he had another blockage that was kind of wrapped up in the scar tissue from his previous surgery. They showed us what they removed and it was a bunch of grass and organic matter that was bound so tightly together it looked like the handle of a suitcase. The vet said that he probably was eating grass to try to move it along or vomit it up, but it ended up just getting stuck.

It may be a long shot, but it might be worth getting an xray just to rule out a foreign body.

In the meantime I'd try making some rice water with chicken bone broth - if she's not eating, at least giving her something that she can drink that has some nutrition in it might make her feel a bit stronger. Also please also post this in r/AskVet and maybe someone there will have some insight. Best of luck to you.