Melissa Ann Shepard, also known as Melissa Friedrich, pleaded guilty in Sydney, Nova Scotia, to administering a noxious thing -- the tranquilizer benzodiazepine -- and failing to provide the necessity of life, the Canadian Broadcasting Corp. reported.
She had been charged with attempted murder after Fred Weeks, 75, fell ill at a bed and breakfast in Cape Breton last September, just a few days after they got married.
The CBC said their marriage was later ruled invalid by provincial officials who said false information was provided on their marriage certificate.
She served two years in prison and then moved to Florida where she met Robert Friedrich. They got married in Nova Scotia in 2000 and a year later his health began to deteriorate and his family alleged his money had started to disappear.
No one was charged after he died in 2002 of cardiac arrest, the CBC said.
Shepard was slapped with a five-year prison term in 2005 for theft and other crimes arising from her relationship with another Florida man she met online, the CBC said.