Hello Nha
Alternatively, you could download the SBB Mobile App on her phone, and authenticate with your SwissPass account; by doing so she could display the tickets in the app. The same SwissPass account can be shared among 3 mobile devices.
In any case, she must have an ID or her SwissPass with her at all times. E-Tickets are only valid with an ID or the SwissPass, this also applies for children.
Best regards,
Roland