Hi, I work with many people with diabetes, hyperglycemia, and hypoglycemia.
Sometimes hypoglycemia is a condition that indicates diabetes may be an issue
later in life. Does mom have any family hx of diabetes? What was babies birth
weight? Is mom overweight?  Anyway, I have no knowledge that breastfeeding
makes hypoglycemia worse.  Find out what mom is eating.  Is she eating a lot
of concentrated sugars?  Drinking a lot of juice, soda, sweet tea?   The best
treatment for hypoglycemia is small frequent meals (maybe 6 a day ex. 8am,
10am,1pm,4pm,6pm,8pm) , combining the carbohydrates, protein, and fat at meal
time.
Avoid simple sugars- sweets, sweet drinks, fruit, juices (especially do not
consume them between meals).  It is similar diet as that for diabetes and will
keep blood sugar from taking plunges.
Good luck!
Melissa Baron, MS, RD, CLC