By now you may have found this info. She could have been one of the "orphan train" children. They were mostly born in NYC and were placed with children's asylums. They were then "placed out" to be adopted or indentured to families in different parts of the country. I believe Minnesota was one of the sates. To find out if she was, you could write:
New York Foundling Hospital
Record Information Department
ATTN: Yvonne Wintz
590 Avenue of the Americas
New York, New York 10011
I am doing the same thing as I try to find out the ethnic origins of my grandfather, Edward A. Terriss (Teraskiewski Edward Alphonsus Terasavage) and Edward A, Terriss. He was adopted in 1900 or 1901 in Shamoken, PA.
How did you find out your great grandmother was born in New York?