@linguafood your description of your friend recalled to me the picky eater self-described in the Guardian article in this thread:
That picky eater actually seemed to have a type of eating disorder called ARFID, that they took treatment for and then got better.
ARFID is a psychological disorder that is recognized in the DSM-5, and is much beyond just picky eating, and is based in a phobia, or anxiety, or texture/taste aversion, or extreme lack of hunger cues, around entire broad categories of food, not just a few things. It can make the person’s life pretty miserable and put their health at risk. Many would like to eat better but are unable to do so without a lot of help.
Not sure if this describes your friend, and I am certainly not a medical professional. But the comparison crossed my mind so I thought I would share.
