Hi,
The dizzy spells must be quite concerning for you. It might be worth heading off to the Dr to get it checked out.
But, as I have said many times before, just because something happens while you are breastfeeding, doesn't mean it is caused by breastfeeding.
Breastfeeding is a normal state for our bodies to be in - dizzy spells are not.
What a dreadful shame your sisters friends were given such poor information that they were led to stop one of the most important relationships in their lives and something that had such amazing health and psychological benefits for themselves and their babies.
Go and get it checked out and treated if need be, but it is not caused by breastfeeding.
Barb