Sinnott played youth football for Boca Juniors of Gorey, then attended University College Dublin on a soccer scholarship.

[3] In November 2011, Sinnott signed for Shamrock Rovers ahead of the inaugural 2011–12 Women's National League season.

She was named player of the tournament in a four-team competition hosted in Castlebar.

[8] In May 2015, Sinnott was called up to the senior national team for the first time, for a friendly in the United States.

[9] Sinnott won a debut cap as a late substitute for Stephanie Roche in Ireland's 3–0 defeat.