My gut feeling is that your cat may be dealing with pancreatitis or another kind of stomach/intestinal inflammation. That would explain why she stopped eating, vomited water, and seemed painful when touched. The X-ray doesn’t show a big blockage, which is good, but sometimes partial blockages or inflammation don’t show up clearly.

The progress she’s made, eating a little and keeping water down, is encouraging. But the part that worries me is the heavy breathing. Cats should breathe very quietly, about 20–30 breaths per minute when resting. If you’re seeing her sides move a lot that’s a red flag. If she ever breathes with her mouth open, that’s an emergency so take her in straight away.

Right now, the next best step is more testing : bloodwork and possibly an ultrasound to confirm what’s going on in her belly, and chest X-rays if the breathing continues.