Getting back to the original question in this thread:

I experienced breathing difficulties a few years ago similar to those
described.  In my case, it turned out that I was developing Type I
diabetes.  Although I never sought direct confirmation of this from my
doctor, I think that the breathing problem was associated with the
presence of ketones due to the diabetes.

I think that ketosis can occur in lesser degree if one is restricting
their food intake drastically.  I don't know if this relevant in this
case, but you might ask your daughter if she has been eating
properly.