Other mistake: The eyebrow on Two-Face's left side is completely illogical. He wouldn't suddenly have an eyebrow that's bigger and bushier than his other eyebrow, and if anything the explosion that created Two-Face would have singed off that eyebrow. The eyebrow is there when the doctor removes Harvey Dent's bandages, so it's not like he put a fake one on for cosmetic reasons, nor would it make sense for the doctor to put a fake one on ahead of his face being surgically repaired. (00:21:15)
Continuity mistake: The explosion that scars Harvey Dent and creates Two-Face is shown to have scarred and colored him light blue on the entire left half side of his face and neck. However, when he is first shown in the hospital, the parts of the left side of Harvey's face that aren't covered in bandages are still normal, as is his entire neck. (00:19:35)
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: The pothole with the mud that Rupert Thorne's henchman kicks at Harvey Dent appears from nowhere. When the henchman is shown kicking the mud, the pothole is located between the police officer behind the henchman's right shoulder and Harvey's assistant Carlos on the henchman's left. However, in the previous shot, the ground shown between the police officer and Carlos contains no pothole. (00:04:35)
Factual error: After he becomes agitated with his doctor, Harvey Dent is able to toss the doctor across the room with one hand while sitting in his hospital bed. Harvey Dent/Two-Face does not possess superhuman strength, and lying in a hospital bed for several days would have only weakened him, so throwing his doctor across the room like that would not be possible. (00:20:50)
Continuity mistake: Harvey Dent's mud stain is different when he looks in disbelief after Thorne's goon says he'll chew and spit him. He's got a stain on his lapel that was never there before and is gone later. (00:04:55)
Revealing mistake: When the paper with Harvey Dent's picture on the hospital bed is burning, there are a few frames with the words "CUT THESE FRAMS" [sic] that can be seen through the flames. (00:20:30)
Continuity mistake: Once Big Bad Harv identifies himself and tosses Thorne against his goons, the dossier is gone from the desk as he poses all menacing, and is back there later. (00:18:10)
Continuity mistake: When "Big Bad Harv" is summoned by the shrink and grabs the coin he tossed, the cuff of the shirt is red instead of white. (00:10:50)
Continuity mistake: As evidenced by the news report that Thorne is watching, Carlos and a photographer by him are looking at Harvey's aggression from two different places practically at once. (00:06:10)
Continuity mistake: Carlos' suspenders are not drawn in the shot before he starts clapping - and the ruffian is getting dragged to the police van. (00:04:45)
Continuity mistake: When a policeman warns Gordon that the SWAT team is in place, there's nothing to the right of the police car; in that spot there was another patrol car, and a policeman with his gun out. He ducked when the villains started shooting, but he couldn't have gone away without any cover. (00:02:55)
Other mistake: Several shots during Harvey Dent's fundraiser show characters in the crowd never blinking or moving a muscle. (00:07:10)
Continuity mistake: When Harvey Dent is walking away from the crime scene, Commissioner Gordon is on his right when next to the police van. Later when Rupert Thorne is watching the news report, Harvey is shown walking by the police van by himself. (00:05:40 - 00:07:00)
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.