Tell her you mean Cryptosporidium serpentis. Find a new vet if she doesn't know what that genus means because this is MUCH more important than just an infection of reptiles. NOT a fungus. Recurrent, but sporadic, regurgitation is the main symptom, and I can't think of a case of Crypto where a snake with THAT large of an obvious sign of gastric swelling didn't also show the regurgitation occasionally. (I'm sure it happens, but it isn't very common.) The gastric swelling doesn't feel like liquid, so if this feels real soft, it almost "has" be something else. Of course, the gastric swelling is likely to look like soft tissue (which doesn't feel soft like liquid) in an X-ray. I do wonder what she expects to learn from the barium if she suspects crypto now. Shrug? Maybe she is looking for an obstruction, but an obstruction wouldn't look like soft tissue in the earlier x-ray.
Anyway, realize a fecal is likely to come back Crypto negative even on a positive snake. The best way to check for it is via a gastric lavage, but even that will often give a false negative in a known positive animal. Biopsy is the only "sure" way of rulling it out, but that's a little drastic.
As far as being contagious, crypto is via an oral-fecal route. It is actually "rather difficult" to transfer from one animal to another unless you move things from one cage to another (this is why I say to NEVER re-use food items that aren't eaten!) like substrate, waterbowls, hide boxes, etc. Crypto is also not the end-all hobbyists tend to think it is out of fear. Combining what I just mentioned with the fact that it is no longer believed to be that rare in the WILD, this is not something to give you nightmares about the rest of your snakes as long as you use proper husbandry techniques from one snake to the next.
It seems to be a naturally occurring infection, but it can go for 15+ years without becoming symptomatic...and will only become symptomatic (many times, anyway) once something else stresses the animal (or the re-infection rate in captivity is exceptionally high) allowing a problem to develop from Crypto. In other words, every single cornsnake colony in America - everyone reading this - could have crypto in their collection and not even know about it - ever. Anyone with any WCs running through at all probably have an EXTREMELY high chance of having it - or of having had it. We just don't know HOW common it is, but we do know it is very common in asymptomatic animals in some wild populations!
Sorry if some of this is a repeat - I didn't read all of the above posts. The main thing is to say, "Sorry about that snake whatever the problem is" and "don't think it is the end of the world if it is Crypto as long as you have taken proper precautions in advance to break the oral-fecal route of infection."
KJ