GERARD Baden-Clay's mistress Toni McHugh says she was convinced that he would marry her 'one day' but admitted she was '"too forgiving'' of him.

In an emotion-charged interview with Channel Nine's 60 Minutes program, the real estate agent, who worked with the now convicted killer, spoke about the future she hoped to have with Baden-Clay.

"I just thought it'd be a normal future, I thought it'd be two people that loved each other," she said.

Journalist Tara Brown asked whether she had hoped to marry Baden-Clay.

"He had told me that he would marry me one day," Ms McHugh said.

Baden-Clay and Ms McHugh, who were colleagues, began their affair in 2008.

Ms McHugh said she never thought of herself as Baden-Clay's mistress.

"I believed that I wasn't that person for Gerard," she said.

"I believed I was in a loving caring relationship that did have a future."

Ms McHugh said she was deeply in love with Baden-Clay.

"I don't like to use that word unconditional any more but I did love him unconditionally and I was very forgiving.

"Too forgiving," she said.