Nope. She's a canon villain who has made a number of appearances in the comics (I don't know for certain if she was in the animated series, but I think she was). She's sorta like Dani Moonstar or Scarecrow in the sense that her power is manipulating people's greatest fears (though unlike Scarecrow she doesn't need any special "fear gas").
EDIT: Looks like this comment was already answered XD
In fact, Phobia is considered one of DC's Deadliest Villains, according to CBR. Her powers would send even the Joker running off and crying for his mommy! In fact...THAT would be a face-off worth seeing (next to Darkseid vs Trigon, of course)!