At first they thought it was from the intubation but since it continued for several days they referred her to a speech therapist which is who handles this sort of thing. Her neurosurgeon gave her actively dangerous advice that both the nurses and speech therapist told her to ignore ("just chew the food more, then everything turns to oatmeal")
It turns out swallowing is really complicated. After neurological damage you get mobility back much more quickly than sensation and since swallowing is very sensation-intensive there was the real possibility that it may never go back to normal. I'm not a doctor so I'm probably getting some details wrong but there's a semi-voluntary component that kicks off the process, then the involuntary actions kick in. The involuntary bit is a delicate ballet of neighbouring semicircles in your throat contracting simultaneously, then one after the other. In her case, some of those semicircles were not firing or were firing at the wrong time, but only on one side. That made food that breaks into particles or is too thin get pushed around instead of down, so it would get stuck in her throat. If you inhale food particles this way, particularly with a weakened immune system, you're at risk for pneumonia so they take it very seriously
The food she could and couldn't have was pretty surprising. She could have shredded chicken, but not ground beef. She couldn't drink regular water, but could have jello (she could handle jello or augur both, though many people with dysphagia can't handle jello because it melts at body temperature and then runs down your throat). She had to have thickened water which I'd never heard of but was in every drug store I checked. She could have soups that were viscous enough, and vegetables that form fibrous strands when you chew them (like celery), as long as they didn't also form tiny leaves (like broccoli). She could have peanuts but not walnuts.
A good friend saw the weird puzzle of which foods she could have as a fun challenge and flew across the country to stay with us for a couple of weeks and experiment. We went through dozens of dishes a day, mostly in small quantity and then scaling it up if she didn't have trouble with it. I've never washed so many dishes in my life
She's fully recovered now but a challenge definitely helps you definitely learn to appreciate the little stuff :)