What did Marguerite do when the Marquis St. Cyr was on trial? plz HELP!!!

From the text:

Marguerite had "inadvertently" caused the death of the Marquis,

"Twenty-four hours after the simple little ceremony at old St. Roch, she had told him the story of how, inadvertently, she had spoken of certain matters connected with the Marquis de St. Cyr before some men--her friends--who had used this information against the unfortunate Marquis, and sent him and his family to the guillotine."