There is no point sending the mother to the doctor, except to rule out
something like a breast lump, which the mother is more likely to find on
her own anyway.  The doctor won't have a clue, likely, about yeast
causing deep breast pain.  He may even laugh at the idea.

It does sound like yeast.  If she weans on that side, the pain will
disappear.  I have one mother that got it back nursing the second baby,
but usually that does not seem to happen.

Jack Newman, MD, FRCPC