Revealing mistake: In the Fredericksburg battle scene, just after the Union officer orders the men to fall back, there is a 1 or 2 second close-up shot of a Confederate soldier taking a hit and falling back. As he does, a modern wristwatch is visible on his left wrist under the sleeve of his coat. (01:49:49)
Revealing mistake: DVD Side B. Just before the cannon burst near General Lee and his officers at Fredericksburg, you can see a Confederate soldier with the sponge rammer using it to the side of the cannon bore. This cannon must have been a actual field piece since the bore in the scene was most likely blocked. The sponge rammer consisted of a sponge-head of elm or poplar and covered with wool. The number one man of an artillery crew drove the sponge to the bottom of the bore and turned it numerous times to put out any embers from the previous firing of the piece. The rammer head was made of hard wood, generally elm or beech. The number two man would place the shell inside the bore, and number one would use the rammer to shove it down the bore with a single stroke. (00:02:25)
Revealing mistake: When the Yankees are moving along the field taking artillery fire, a shot shows a shell landing in a group of men, in which a few go flying. When one lands in front of the camera, you can see the ground lift up and the sound of him hitting the mat instead of the ground. (On Disc 2). (00:08:10)
Revealing mistake: When Lee, Longstreet and Jackson are riding through the streets of Fredricksburg, just after the old man has spoken to them, the damaged houses in the background are obviously from a painting. Easiest way to tell is that the street is full of people, up until a certain point. (00:28:25)
Revealing mistake: Towards the end of the movie, as Jackson's Corps is attacking the exposed Federal right flank during the Battle of Chancellorsville, when the Confederate forces begin overrunning the Federal encampment, they sweep past two artillery pieces. Notice the second gun - it has a blocked barrel (filled with concrete). Must have been a memorial piece that was on/near the Chancellorsville battlefield.
Revealing mistake: When Jackson and his entourage ride in front of a big house at what he is told is Chancellor's Crossing, there is smoke coming out of the chimneys, especially the one on the left. Jackson and Jim stay there for almost 19 seconds and the smoke never moves, neither rising or blowing to the side as real smoke would. Obviously the house and background are a painting. (01:50:52)
Revealing mistake: As Jackson and his men ride up to a big house which he is told is at Chancellor's Crossing, there is smoke coming from the chimneys, especially the one at the left. The scene goes on for over 15 seconds and the smoke never moves. Even on a bitter cold night the smoke would rise and move even if slowly. Obviously the big house is a background painting. (01:50:00)
Answer: Yes, she did exist. Through books.google.com, I found a book "Cemeteries of Caroline County, Virginia: Private Cemeteries" by Herbert Ridgeway Collins, that confirms Jane did live, that she and Jackson were close, and that he arranged for her burial after her death.