WPMU DEV Dashboard client access

Hi,

We need to avoid our client to see our details (subscription details, activity on forum, profile, etc) in the WPMU DEV Dashboard plugin. We have enabled the option for only our admin user to have access to it, however upon deleting our admin user, the client's admin user can access the WPMU DEV Dashboard again (seeing our details).

That's your recommendation / workaround to avoid this?
Thanks!