Speaking to chat show host Graham Norton, she said: "I know a lot of us in it, when the producer said they were thinking about number two, thought 'It was great, leave well alone.'
"But then they talked us through the idea and we all said 'Oh, that's very good.'"
The gripping murder mystery depicted the lives of locals living in the small seaside town of Broadchurch, in the wake of the death of one of its young residents, and the subsequent murder investigation
ITV announced the programme was returning shortly after viewers saw the murderer of schoolboy Danny Latimer unmasked in the final episode of the first series.
The final part of the popular drama saw a peak audience of 9.3 million.
The new series of Broadchurch is due to go into production early next year.