Is she spayed? Intact females will pull hair from their dewlap to make a nest if it’s a false pregnancy

Is there any wetness in the area, or have you noticed her drooling? Excessive drooling can cause fur loss. A Netherland Dwarf can be more prone to dental issues than some other breeds. If you notice wetness or drooling or trouble with eating certain foods, then she may have a dental problem.

Also has your bun been treated for mites! They can cause bald patches but are virtually invisible to the naked eye.

Wait is that really true? My Flemish Giant named Oliver always had this bare spot of fur behind his head and ears. I’ve never seen him scratch himself that much, and I’ve never gotten mites before. Could it be that he used to have it, and the hair never grew back?

(Sorry that’s another question and not an answer)

I agree with the others. Those are all possibilities.

creepycrepes – Thinness on the back of the neck is normal, particularly in younger rabbits.