Trellis + Bedrock + Digital Ocean

Thank you for this forum, I was able to launch our website 4 months ago.

Now I am having an issue having additional person to have access to droplet in DigitalOcean. We have a team account in DO. She already added SSH. She has an owner access. Yet she is not able to access the site through SFTP (PuTTY)

Am I missing something? Do we have to run some command in console to add her, somehow?
This is something I was wondering about it before I launched the site.

What is the best way to have other people accessing the site through SFTP?