Based upon all records found, she was known and identified as Mary Ann. While Ann is a second name, I do not think it was used as such.
New York Census: 1905, 1915
This week's featured connections are Redheads: Mary Ann is 27 degrees from Catherine of Aragón, 26 degrees from Clara Bow, 35 degrees from Julia Gillard, 23 degrees from Nancy Hart, 24 degrees from Rutherford Hayes, 27 degrees from Rita Hayworth, 29 degrees from Leonard Kelly, 30 degrees from Rose Leslie, 28 degrees from Damian Lewis, 27 degrees from Maureen O'Hara, 33 degrees from Jopie Schaft and 42 degrees from Eirik Thorvaldsson on our single family tree. Login to see how you relate to 33 million family members.