Change the “Affiliate” text to say something else such as “Refer a Friend”.

There is no options to do this currently in the plugin.

However this can be done via a translations plugin such as Loco Translate. See here for details.

Alternatively, you can potentially do this by adding a custom code snippet to your site.

Here is an example:

add_filter('gettext', 'change_affiliate_to_refer_a_friend', 10, 3);
function change_affiliate_to_refer_a_friend($translated_text, $text, $domain) {
  // Check if the text domain matches
  if ('woo-coupon-usage' === $domain) {
      // Change "Affiliate" to "Refer a Friend"
      if ('Affiliate' === $text) {
          $translated_text = 'Refer a Friend';
      }
  }

  return $translated_text;
}

The above code will change “Affiliate” to “Refer a Friend”.

How to add custom code: https://www.wpbeginner.com/plugins/how-to-easily-add-custom-code-in-wordpress-without-breaking-your-site/