<< MD has been called several times, says it can't be yeast because there are
no white spots on the nipple, and that the pain is coming because her breasts
are heavier with the milk.  >>

Ann,
Yeast is not always visible, on the nipples, in baby's mouth, and of course
not in the ducts!  It sounds very much like yeast to me, as shooting pains
are typical.  You might look for other indications of yeast, like diarrhea in
the baby or a rash.  You might ask about her use of antibiotics in the past
few years.  And does she crave a lot of sweets?  These can all be indicators
of yeast buildups.
     Also, some strains of yeast are resistant to Nystatin, so she might see
about an alternative prescription drug.  Yeast within the ducts like that
would not respond to something applied topically (Gentian Violet, you
 mentioned), so she should look more to oral treatments.  If she has had the
problem for that long, and it is indeed yeast, she really should look into
some dietary changes as well.  Avoiding sugars of ANY form, and adding
lactobaccillus acidophilus may be of help, and possibly garlic.  Dr. Crooks
books about Yeast (The Yeast Connection) may be of interest.

Hope this helps some, and I'm looking forward to seeing others'  posts.

Constancia Wendt, LLL