She explained it in an earlier picture -- in the Japanese version of the comic, Tails's gender was never actually specified, so Zenox is taking a little artistic license with it. Tails grows up and is a lady.
Have you ever watched a youtube poop, or know about the Philip Cd-i Mario and Zelda games yet? Because this is a Zelda Cd-i joke. If you have no idea I'm talking about then go look up Mario Cd-i or Zelda Cd-i to one of infamous games to feature Nintendo characters!