To Marilee re Mom of baby with cardiac problems and others. I feel for you.
In an artical in the (Australian) MEDICAL OBSERVER on 28 October 1994 was
printed 'Hindmilk best for premmies" by Don Radcliffe.  I quote " The new
feeding strategy requires expressed breastmilk to be divided into two
portions; foremilk and hindmilk. The foremilk, or initial milk is collected
and frozen for later use. Low birthweight infants are fed the hindmilk,
which is three to four times higher in fat."  It seems to be that your Mom
is instinctively doing what 'science' suggests.
This artical states this technique was reported in the JOURNAL OF PEDIATRIC
GASTROENTEROLOGY AND NUTRITION August issue. I would think American Journal.
A. Stolz. RM IBCLC Queensland Australia.