Heffernan left school at 14, in 1956, to begin working for her father at his Dunnes clothing shop on St Patrick's Street in Cork, which he had founded after leaving the chief buyer position at Roches Stores.
[4] She took a leading role in textile buying, and later also strategy,[4] and once sent her brother, then CEO, back to reverse a £20 million deal for cheap shirts of which she did not approve.
She also developed a reputation for tough negotiations with outside parties, including unions, with the company involved in 448 legal actions in a five year period.
[10] Ben Dunne Jnr was again embroiled in scandal in the mid-1990s when it emerged he had given large amounts of money to a number of Irish politicians, mainly from the Fianna Fáil party including the then Taoiseach, Charles Haughey.
[2] As part of this, she engaged designers such as Paul Costelloe to produce dedicated lines for Dunnes, and media gardener Diarmuid Gavin to provide complementary offerings.
[13][4] Heffernan helped set up The People in Need Trust in 1988; it has subsequently raised tens of millions of euro, with a focus on supporting local charitable activity.