Drupal7: Rules Module - change the FROM field
I finally figured it out.
You can edit the "Send mail" component of the Entityform rules at:
/admin/config/workflow/entity_rules/entityform_submission/manage/rules_entityform_notifications_email_send

Then specify the value of the FROM field from the replacement patterns.
Keep in mind, when you build the form, or any new future forms, make sure that you always use the same field for the email and make it required. An empty email will result of the FROM field being sent from the site-wide admin email and not from the user's email.
See image, hopefully it helps: