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.
If you’ve been entrusted by a family member or close friend to file their taxes for them using NETFILE, you can certainly do so in TurboTax. Ideally, the taxpayer (i.e. the person for whom you’re preparing a tax return) makes a final review of their return and together you transmit the return to CRA’s NETFILE service.