Jo Anne,
In response to your mom nursing a toddler and adopting I don't know of the literature out there.  I only have a sample of 1 of wet nursing my sisters infant.  
My toddler was 8 months old when my sisters 5 week old came to live with us due to my sisters severe post partum depression.  I am not sure how the milk composition changed but it took less than 3 days to have a very abundant supply.  It was very similiar to the same time frame as having given birth again.
I couldn't go more then 4 hours without becoming very engorged.  My toddler was receiving table food at the time as well but I totally bf my niece for the 3 weeks that she lived with me.  
I hope this helps her in some way to have confidence in herself and her body's wonderful abilities.
Donna Goggin-Dolwick

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