Source: 1880 US census, where she is given as the 36 year old sister-in-law of Samuel Gray, with whom she is living in New York. The 1880 census describes her as suffering from malaria on the day the census was taken! This may explain why she has no occupation in that census.
She is also there with Samuel in the 1870 census.
In 1870, she witnessed the marriage of Margaret McVicker, who I believe was her sister, to William Gray. Her other sister, Sarah McVicker, was married to William's brother, Samuel Gray, the other witness at the wedding, and they also lived in New York.