I don't know why this drug would be used for hair loss in women.  It is
used for the treatment of advanced prostratic carcinoma.  There might be
a theoretical rational for using it in men, but I doubt that it would
work, from the information I have.  If I were this woman, I wouldn't
touch this drug.

Many women lose an awful lot of hair between 3 and 7 months after birth.
It has *nothing* to do with breastfeeding.  Bottle feeding women also
get hair loss, sometimes quite dramatically.  Here from Conn's Current
Therapy, under Telogen Hair Loss "By far the most common event causing
telogen hair loss is childbirth (note, not breastfeeding).  Usually the
baby is 4 to 5 months old when the hair loss is discovered, and is
walking and talking by the time it has *spontaneously* resolved.  No
treatment except reassurance is reuqired or helpful".