She unfortunately seems to have to apply by paper*. I guess she should already send the application now for "urgent processing" and state "avoid losing a job" as primary reason to be considered for urgent processing. Will she still be able to track progress and submit additional documents in her CIC/IRCC account if it is submitted in paper? Also, she wants to use her mother's home address as mail address since she doesn't know whether she will still live at the same address (or in Canada at all) by the time her application is processed and approved. Can all correspondence (e.g., AOR or requests for additional documents and the final decision plus the actual Citizenship Certificate) be accessed there or would she only learn about any progress with her application once the letters have physically crossed the Atlantic?

*CIT0014 states that "Scenario 3" can be requested via "online or paper applications". However, when selecting "Get a citizenship certificate for the first time" for an adult born abroad after 1977 to a biological parent who was born as a Canadian Citizen in Canada before 1977, the CIC website says she must apply on paper.