"I went through the process of having my marriage declared null," she told a session on Christ as the "unifier of a blended family."
During her presentation, given in French, she said she had always kept this fact hidden from her public life.
"Yes, I lived a legal divorce. Then I turned to the Church and asked if my marriage was valid. The answer was 'no,' ” she told the people at her conference.
"I touched God's mercy through the process of having a declaration of nullity for my marriage," she told Catholic News Service. "Christ still loves us, whatever our family situation may be."
When her husband left her, she had three children under the age of 11. She said the Montreal priest she talked to told her: "'You are now being called to heroism.' He had the guts to tell it straight to me. Has it been a hard experience? Let's just say it's not what I had dreamed about. But I raised my children with the Lord's help."
During her presentation, she spoke about how Christ strengthens families and how parents must teach their children to answer God's call in all the aspects of their lives.
More than 17,500 participants from more than 100 countries registered for the Sept. 22-25 World Meeting of Families. Pope Francis is scheduled to participate in the Festival of Families Sept. 26 and celebrate Mass Sept. 27 on the Benjamin Franklin Parkway.