As others have pointed out, what was the result of the DUI - conviction, lesser charges, etc... Even without any jail time, she risks being inadmissable to Canada if she was convicted of a DUI. What Canada does ask whether the offence is "indictable" and can turn you back.

I can't remember whether T1 normally does a full passport screen or not if you go through Customs B (from US to int'l). Unless you can interline your bags, you'll have to go through the normal immigration process, where your sister will be put through the normal immigration screening process.


Your sister's trip is at real risk if she was convicted of a DUI (vs something less serious). Get the facts figured out and make sure to have the paperwork if she was only convicted of a lesser offense.

See this link http://www.canadainternational.gc.ca....aspx?lang=eng (it is for Australians but the concept applies)