After university, she taught in a large comprehensive school in inner London, before becoming headmistress of St Marys Convent in Cambridge.
After emigrating to South Australia, she taught at both St Ignatius Secondary School and St Francis of Assisi Junior Schools before making a change to health, community and disability sectors.
Simmons first ran as a Labor candidate for the division of Sturt against Liberal incumbent Christopher Pyne at the 2001 federal election but was unsuccessful.
Generally occupying the same area as Sturt, the new state seat of Morialta to replace Coles was won by Liberal incumbent Joan Hall on a two-party vote of 54.1 percent at the 2002 election.
It was the first time a Labor candidate had won Morialta or Coles since Des Corcoran at the 1975 election.