Install Drupal into a different directory than drupal-vm is installed
You can override the default configured webroot directories by altering the local_path property in the vagrant_synced_folders array with a custom config.yml file (copy over default.config.yml if you don't have one).

Per default.config.yml:

# A list of synced folders, with the keys 'local_path', 'destination', and
# a 'type' of [nfs|rsync|smb] (leave empty for slow native shares). See
# http://docs.drupalvm.com/en/latest/extras/syncing-folders/ for more info.
vagrant_synced_folders:
  # The first synced folder will be used for the default Drupal installation, if
  # any of the build_* settings are 'true'. By default the folder is set to
  # the drupal-vm folder.
  - local_path: .
    destination: /var/www/drupalvm
    type: nfs
    create: true