I'm so sorry you're going through this.
How is she today? Sometimes it does take a day or two for the anti-nausea drugs to kick in.
Depending on where you live, have they tested for blastomycosis? I believe it can cause tumor-like lesions, although I'm not sure if it can appear that way in the intestine.
Also, are you anywhere near a veterinary teaching hospital? We had a dog that was eventually diagnosed only after we got a referral to the VTH at the U of Minnesota. They see so many tough cases at the teaching hospitals that they often can diagnose things that regular-practice vets miss. Although they can be a bit more expensive, having a diagnosis was worth it to us, and once on proper treatment, our dog improved. So if there's one within driving range, that might be a good place to visit.
Best wishes for you and your girl. Please keep us posted on how she's doing.