You can lie, and pretend to be your Mom. If anyone asks, she can say that she did it but had a bit of help.
Or you can do it the proper way - apply to represent a client, login as yourself, and give her SIN. I forget the exact detains but they're all spelled out in the CRA's website.
https://www.canada.ca/en/revenue-agency/services/e-services/represent-a-client.html
You can use TurboTax to file a tax return on behalf of someone. Technically speaking, the CRA’s NETFILE service is for people who prepare and file their own returns and is not intended for people filing returns on behalf of others. But, it's understood that many people trust their spouse/partners, friends and family to prepare their returns for them.
For people who file tax returns on behalf of others professionally and use the CRA's E-File service, it is recommended you use professional software such as Intuit's ProFile. You can then apply for a Representative Number which will allow you to obtain information on behalf of clients and use the CRA's AutoFill My Return (AFR). As an E-filer you must also register and be approved for an E-File number that allows you to file on behalf of these clients.
Please see this link for more information: Can I use NETFILE to file someone else's tax return?
This reply (from Support) needs to be posted in the FAQ and on the community website. It should also be clear to clients that buy a package capable of filing "20 returns" that with CRA's new requirement for 2FA, you have to have the family member sitting beside you so that they can receive the 2FA challenge and provide the response to you to enter. Otherwise, you cannot download their T-Slips or NETFILE for them.