Kathleen,
When visiting my cousin this summer, her husband (a neurosurgeon) related
this to me.
He had a woman see him for possible surgery for a pituitary tumor (she was
experiencing sudden unexplained lactation and her children were teens!) Tests
showed no physical evidence of a tumor so he asked her about her sexual
foreplay practices with her husband.  It turns out that this woman's husband
used EXTENSIVE nipple stimulation during foreplay thus creating a milk
supply! Could this be the case with your mom?