Short visits for meetings and observation may continue as before, but she should not begin performing the U.S. role until the petition is approved and she is admitted in L-1A status. Doing the job on visitor status undermines the case.
Do not start the job before the status exists
A pending petition does not change what the manager may do on a business visit. Attending meetings, reviewing reports and consulting with the U.S. team remain visitor activities; taking day-to-day charge of the plant, supervising U.S. staff on an ongoing basis and drawing U.S. salary do not. If the company needs her in place before the approval, it should either file with premium processing to shorten the wait or arrange for an existing U.S. manager to hold the role in the interim. Because the L-1A petition is filed with USCIS and a Canadian citizen can then be admitted at a port of entry with the approval notice, the timeline is governed by USCIS processing rather than by a consular appointment. Build the start date from the approval, and keep the monthly visits brief and documented while waiting.
Hypothetical example: a library-systems supplier needs its Canadian regional director in the United States for a product launch. The sequence begins with confirming the related companies and the person's qualifying foreign year, then preparing the petition with a realistic managerial staffing plan. The approval process, not the launch announcement, controls the work start. Visiting for meetings may be different from taking over the U.S. director's daily duties, so the company should assign those duties locally until admission. Count the director's earlier L time before promising a term, since the L-1A total cannot exceed seven years.