Hi. You cannot bave a Sonos account each and don't need it. Don't think of it as your Sonos account; think of it as THE Sonos account.

You should both log into the same system from the Sonos apps on your respective devices.

You can both add your own Spotify accounts or whatever. Just add them from your own devices.

The question is indeed what you want to achieve with your wish.

Thanks very much for your answers. We’ll figure out how to add her Spotify account to our Sonos account. 

You should use her phone, connect the app to your existing system and then add her Spotify account to the system using the usual add service procedure.

Each controller can default to the owner's Spotify account, but all users can access all Spotify accounts. 

Voice control will access the last account that was used on this speaker, so there can still be a bit of confusion left……