Continuity mistake: The mud stain on Harvey Dent's suit disappears when he assaults the henchman that kicked the mud on him and then reappears when he is walking away from the scene. (00:04:50 - 00:05:50)
Continuity mistake: When Harvey Dent wakes up from his nightmare, his face is sweating profusely. A couple of shots later and there is no sweat to be seen on his face. (00:02:10)
Answer: She escaped off-screen and created a copy of herself to fool everyone.