I had a look at the children's names of the couple Mulder / Van den Bos and I think this is your Mary.
Martje van de Bos born 24-Sep-1870 Westernieland ( Eenrum )
daughter of Kornelis van den Bos and Barbera Dijkema.
Kornelis is the brother of Folkert.
This family arrived 02-May-1889 in the USA