For background:
According to the 1910 census, when they are living in the same household, she only arrived in 1900, whilst he was living there since 1866. He was a naturalised citizen working at the Star of the Sea Church, and she assisted him.
Also, both in South Dakota in 1905 census, with an estimated arrival date for her of 1899 (index only, not images)
Added:
Both together in 1900 census, with a few more nuns, in Lead City, Lawrence, South Dakota.