Marriage gives no status in Canada. However, if she marries a PR and they apply as an "Inland" application, it can give her Implied Status. (But not always.)
If they apply as an "Outland" application, she would need to leave Canada or risk being deported. She could techincally stay, but will have explaining to do when she tries to land from inside Canada. She would also be lying on her application about her location, address, and status. That would be grounds to reject her visa.
Did she apply for extend her stay as a worker or a visitor? It's best she file for a restoration of status (if needed) and a visitor's visa asap. That way she can remain in status until she and her husband apply for her PR visa. The government can and will deport her if they chose, even if she's married to a PR or citizen. Even with an Inland application, it can take 2-3 months to prepare the application after the marriage. By that time, she can expect a departure order from CIC in her mailbox.