Continuity mistake: When Riddler burns his costume, he's wearing his purple gloves, but after throwing his green jacket into the fireplace, his gloves disappear entirely. (04:25:03 - 04:29:59)
Continuity mistake: The soles of Batgirl's boots change from light to dark blue throughout the episode.
Continuity mistake: Batgirl's boots gain and lose heels throughout the climax of the episode.
Continuity mistake: Riddler's gloves disappear briefly after Batman confronts him at his party.
Continuity mistake: Both of Harley's shoes are red as Batman holds her after rescuing her from falling.
Continuity mistake: Two-Face's left leg is blue here whereas it was normal in part 1 of his origin episode.
Answer: She escaped off-screen and created a copy of herself to fool everyone.