Ottawa has sent a diplomatic note to the Mexican government, in the hopes of clearing the way for an imprisoned Canadian woman to return home, CTV News has learned.

Foreign Affairs Minister Maxime Bernier has also appealed to his Mexican counterpart for the woman's release.

Brenda Martin, 51, has been inside a Mexican prison for the past two years. On Monday, she was transferred to the hospital ward and placed under a suicide watch, after a constitutional challenge to her continued imprisonment was denied.

"She fluctuates between being extremely withdrawn ... to begging and pleading for somebody, anybody, to please help her," said Debra Tieleman, a friend.

"Mentally, she's really a mess ... I don't know how much more of this she can take."

Martin, a native of Trenton, Ont., has been charged in connection with a fraud carried out by former boss Alyn Richard Waage.

Martin has proclaimed her innocence and Waage backs that claim. Although Martin has been charged with money laundering, she has not yet been tried or convicted.

Tieleman said Martin was initially interrogated by "federales (federal police) without benefit of either a lawyer or interpreter." That claim was the focus of Martin's constitutional challenge to have her charges dismissed.

Canada's secretary of state for foreign affairs, Helena Guergis, has said Canada can't interfere with Mexico's judicial system.

But she said she has spoken with Mexico's ambassador to Canada, to voice her concerns over the length of Martin's imprisonment.