Having a daughter with this disorder I can just say that, its not childish. Her disorder has been referred to as "food phobia" which explains it fairly well: She does not like a lot of food, but she actually _wants_ to try taste it and get better. But even when doing that, it doesn't really work for 95% of food, she just wont get better at eating it.
It was also mentioned that she is probably on the spectrum, but either she is very far down or she is very much a "girl" and hides it really well because she is diametrically different (play pretend is her favorite pastime, and also pretending to be others etc, also very social.) from how you are supposed to be on the spectrum, but in some ways she shows it in a classic way (change is very hard).
Not for nothing, but this subthread has finally given me a name for my own eating disorder. I'm almost 45 and in the last 10 years I've made some progress towards eating like a normal human being, but from childhood until I was almost 35 the stuff I'm reading about this disorder describes me incredibly closely. I grew up with food allergies (tree nuts, some seeds) and somewhat abusive father (he would get frustrated with me and hold me down and shove food in my mouth—obviously that didn't help matters any and I honestly believe that provided the impetus for most of my "origin story".)
This is something that affected nearly every aspect of my life. I didn't go to college away from home because I was afraid of cafeteria food in the dorms. I didn't join the military because rations. I never took a semester or year abroad because foreign food. Many of my relationships ended because seriously, how many times can a normal person eat bread and cheese in a week for years on end?
I'm sorry to unload here, I'm just reeling from having a name for this. I'm painting a picture here that is pretty bleak, because from the outside it definitely looked that way. I hope you're able to help your daughter move through it. The world today is far more accommodating than the one I grew up in though, so I'm sure her experience is somewhat different.
I also can't eat dairy or wheat for intolorence reasons. Its hard to live live a normal person sometimes. You try to date but can't go to a restaurant confidently (big cities are better though). Most sauces and prepped food have either wheat or dairy. Alcohol in in UK doesn't need an ingredients list either.
I would have sworn blind that I have a physical reaction to these two ingredients. I recently got prescribed some melatonin (it's only available on prescription in the UK) and noticed it had lactose in. I fought for the NHS to perscribe me my usual brand, which has worked fine for me in the past. When I looked, it had the same amount of lactose in as this new prescription.
This really shook me. I know the mind is powerful and can manifest physical symptoms, but to have been "tricking" my self for so long was very eye opening. I'm going to try to get someone to crush up and randomise the new and old meds to see if I can tell the difference blind.
I'm starting to think this has been a mental condition this whole time. I would have bet all I had that it was a real illness a week ago.
Depending on the amount of lactose and intolerance, your body may be able to process a small amount of it(such as in a pill) versus the amount in a glass of milk. It's not a purely binary function.
A lot of the stereotypes around AS are just that. I have two sons on the spectrum and both have traits they are "not supposed" to have and yet strongly evidence other traits so that the diagnosis is clear. In my experience this is even more the case for females. That said, the "food phobia" you describe is by no means restricted to ASD.
It was also mentioned that she is probably on the spectrum, but either she is very far down or she is very much a "girl" and hides it really well because she is diametrically different (play pretend is her favorite pastime, and also pretending to be others etc, also very social.) from how you are supposed to be on the spectrum, but in some ways she shows it in a classic way (change is very hard).