Although I don't have any research papers or references for you, I
have geographic tongue which appeared after my second son's birth.  The
information I could get at the time was that there isn't much known about
the condition at all.  Some people get it and it resolves on its own in four
or five years.  I have had it ten but it does seem better these days
although the tongue is still thickened compared to other people and is
sensitive to some foods.  On days when it is irritated it actually impares
speech.  It has also been suggested that salt and caffeine are culprits, but
again no references.  Nobody suggested it had anything to do with
breastfeeding and I had previously breastfed my first son without it
developing. I was  pregnant or breastfeeding for all those years up until a
year and a half ago but the tongue is still ugly. Certainly I avoid
irritating foods, like crunchy sharp foods, cantalope, kiwi's, and acidic
fruits but going almost completely salt and caffeine free for over a year
did not cure it(although it became less ugly looking and sensitive). If you
find a cure please post it.  If she believes in homeopathic remedies she
could try that.  Hope that helps.

Jennifer Molavi