I only can find grit at feed stores as well tractor supply and farm and fleet carry it. Independent feed stores may also carry it.
I would say after she has eaten see if you can feel her crop any place. If you can then it's not her crop. If you can't it likely is.
If it isn't her crop I'm wondering if it could possibly be an infected feather follicle. I had an English Orpington rooster get one once although his was lower down. We stuck it with a needle to confirm and lanced it and pulled out the infected feather growing the wrong way.
He never had the problem again.
I would rule out all other options first though.
Btw I forget did you mention if this area is hot/warm to touch? And does her beak have any kind of odor coming from it when you smell it?
I would say after she has eaten see if you can feel her crop any place. If you can then it's not her crop. If you can't it likely is.
If it isn't her crop I'm wondering if it could possibly be an infected feather follicle. I had an English Orpington rooster get one once although his was lower down. We stuck it with a needle to confirm and lanced it and pulled out the infected feather growing the wrong way.
He never had the problem again.
I would rule out all other options first though.
Btw I forget did you mention if this area is hot/warm to touch? And does her beak have any kind of odor coming from it when you smell it?