When Ash & Co. arrive on the island they meet Melody. All Melody knows is Ash's name(she's told his name) and that he's a pokemon trainer(she's told that, too). Yet, she calls Misty by name, Without being introduced.
This is just a plot hole that frequently show up in many Anime when a character's lips are moving, but the translators can't think of anything else that makes sense to put in there.