She represented the South constituency in Ireland in the European Parliament from 2004 to 2009.She is secretary of the Hope Project, a charity that helps people with disabilities.
Sinnott founded the Hope Project in 1996.
She married Declan Sinnott when they were both aged twenty one, and had 9 children (3 daughters and 6 sons) together, they are now separated.
In 2000, she took a court case to force the Irish government to provide a primary school education for her son Jamie who has multiple disabilities.
In 2001, High Court ruled that every person in Ireland had a constitutional right to free appropriate primary education based on need.
The judgement confirmed that this was a fundamental right which was not limited by the availability of resources.
The government did not challenge the High Court decision for children 18 years and younger but successfully appealed its application to persons over 18 years of age to the Supreme Court.