User blog comment:FairyRaven/Fairy Tail Chapter 421: Wendy and Chelia, Review and Commentary/@comment-24039250-20150224014538/@comment-7418318-20150224084324

Speaking of Mavis... I wonder if she is invisible to Wendy and Carla now that they no longer have a Fairy Tail guild mark.

She did say that only those with the mark could see her, but we never learned if this anti-invisibility thing sticks to former members too.