Continuity mistake: When we get to the public library the first time there is a shot from behind the homeless guy - he has his hand on a cart. When it cuts to a front shot his hand is off the cart. (00:44:25)
Continuity mistake: When the tidal wave is about to hit Manhattan, Sam and his two friends are walking up the stairs, and the black friend's hood is over his head, but in the following shot it is no longer over his head. (00:46:35)
Continuity mistake: When the huge tidal wave hits the bus you see a man standing on top of a taxi, number 7Z22, which gets crushed by the water. Moments afterwards you hear the French woman saying that she left her bag behind. If you look on the right side of Laura you can see a still intact taxi with the number 7Z22 on it. (00:47:30 - 00:48:00)
Continuity mistake: Just before the huge wave hits the library, we see that Laura cuts her leg. She cuts it on the side of the top part of her leg. Later in the movie, when her trouser leg is pulled back to reveal the wound, it is now on the front of her lower leg. (00:47:50 - 01:30:15)
Continuity mistake: When the tidal wave is hitting Manhattan, and the camera cuts to Laura walking behind the black woman and the cop, the woman panics and turns to her left to look at Laura, but in the following closeup she turned to her right to look and talk to Laura. (00:47:50)
Continuity mistake: As the massive tidal wave is rolling through Manhattan, when it cuts to Sam looking at Laura from the steps, the two taxis in front of the library are further away from each other, than in the following shot when Sam has to jump on the cars just to get over them. (00:48:00)
Continuity mistake: When the wave is hitting the city, there is one bloke standing by the library who is watching the camera. Camera cuts to another view, and the bloke has disappeared. (00:48:45)
Continuity mistake: In the scene when Terry Rapson is looking at his grandson's drawing, Simon comes into the room and puts a cup of tea on the desk. In the first two shots you see that the cup is in the same position where the handle is facing exactly towards the camera, but in the third shot, it has changed position, and the handle is now pointing to the left. (00:49:25)
Continuity mistake: After Sam's phone call to his dad, when Jack holds his wife with both hands at her cheekbones the position of her hair changes from under his hands to over, between shots. (00:56:20)
Continuity mistake: When all the people are in the library sheltering from the cold, in the overhead shot of the guard (the one who told the homeless guy he can't enter the library with a dog), he is in front of Laura and then walks to his right with clothing/blankets in his hand, but in the next shot he is behind Laura and the black cop. (00:58:40)
Continuity mistake: When Jack is briefing the President, he draws a line on a map of the U.S. and tells the President to have everybody south of that line evacuated. The shape of the line changes between shots. (01:04:20)
Continuity mistake: In the scene where Sam smashes the vending machine in the library, you see him first take out about three items from it, and then in the next shot you see him holding two items, but when he throws them onto the table there are about a dozen packets of sweets and crisps. (01:11:25)
Continuity mistake: When the students are looking around the library for books to burn, it cuts to a girl and man standing on the balcony beside a book cart. When the guy reaches across to grab a book and says, "We can't burn this one..." he is holding the book with both hands, but in the following shot his left hand is on the book and the other hand is on the cart. (01:11:35)
Continuity mistake: When Lucy is saying good bye and hugging her co-worker, she puts her arm over the co-worker's shoulder. When it cuts, Lucy's arm is gone and when it cuts it's back over her shoulder. (01:13:15)
Continuity mistake: When T.J. is talking with the homeless black guy who is sitting on the floor telling the student how to keep warm, the guy throws the student a book to rip up and make himself warm. When he throws the book, the student is grasping the book at the bottom with his left hand, but in the following shot his left hand is at the top of the book. (01:16:30)
Plot hole: When you see the shot of New York, just before the scene where the apartment lights go out, there are no lights on in the buildings, or car lights in the street, although it is dark. The lights should still be on as there has not been a power outage. (01:28:00)
Continuity mistake: Sam smashes the window on the boat to get into the medical room. Glass is left in the frame, however. Camera does an instant cut and the glass has gone completely. (01:30:00)
Factual error: When the International Space Station is shown, it's spinning. The space station doesn't spin. The centrifugal force would create gravity on all the outer sides of the space station - and make it impossible to dock other modules. (01:30:45)
Continuity mistake: When Sam and the other two students are on the big ship, Sam goes outside so that the wolves will chase him, locks the door, then climbs the ladder to a door where the students are. The black student is startled and turns around with a metal scoop to his right getting ready to sling it, but in the following shot the scoop is over his left shoulder. (01:34:20)
Continuity mistake: When Jack arrives in New York he's right next to the Statue of Liberty. When the camera pans abowe the Statue of Liberty, you can see that front of the Statue is in light, and it's back in shadow. In the next shot front of the Statue is in shadow, and back in light. (01:42:35)
Answer: She is indeed alive. Take a close look at the scene when Jack Hall arrives. Judith appears in that scene.