Continuity mistake: The bear strikes his left paw at Young Tristan, and he stabs his knife in the paw, but when the bear leaves, he limps on the right front leg. (This is also mentioned on the production designers' commentary track.). (00:05:20)
Continuity mistake: When the young Tristan is wounded by the bear, his arm gets hurt and the sleeve of his shirt torn. When his father treats a few seconds later the sleeve is intact again and the wound seems to be on his chest. (00:05:50)
Continuity mistake: When young Tristan gets attacked by the bear he looks for cover behind a huge tree. In the fight he cuts off one of the bear's claws which falls to the ground. When his father, brother, and One Stab come to help him Old Stab finds the claw on the opposite side of the tree. (00:05:55)
Continuity mistake: After Susannah's arrival at the ranch she takes a walk around. When she passes by the Deckers the sun has already set. In the next shot, when she talks to Isabell Two, the sun is shining again. (00:12:40)
Continuity mistake: When Suzanna comes in for dinner the first night there, all the guys raise something to give her, but Tristan goes to raise his plate. But cutting back from her reaction, he has only lifted his glass to drink. (00:15:20)
Revealing mistake: On her first evening at the ranch Susannah watches Tristan breaking in a mare. When he falls on the ground you can see that he merely climbs off instead of being thrown. (00:18:00)
Continuity mistake: When Tristan and Samuel talk about premarital sex, some strands on Tristan's right temple hang down or are tucked behind his ear alternatingly. (00:20:30)
Continuity mistake: Just after Samuel and Alfred say that they are going to enlist, Samuel has a weird looking face and notice Alfreds shoulder right behind him, then Susanna takes a few steps up the stairs very sad and Samuel walks a couple of meters towards her and then she leaves and then it switches to Samuel with the same funny looking face and Alfred is again right behind him. (00:24:20)
Continuity mistake: In the farewell scene when the boys are leaving to enlist in Canada, we first get to see Samuel hugging Decker and Alfred hugging. Behind Alfred's neck we get a glimpse of Isabel Two's head as she is jumping up. This can only be Isabel Two approaching Tristan. In the next shot we get to see this again as the camera focus on Isabel Two running towards Tristan and jumping up into his arms. (00:27:25)
Factual error: The three Ludlow sons were leaving for England on October 14, 1914. When they were walking outside guiding their horses, the small trees in front of the house had green leaves. In Montana, Fall foliage typically begins by early - or mid-September. In most of the state, there should be peak Fall foliage (yellow/orange/red leaves) by early - to mid-October, not green leaves on the trees. Also, some time later when the sons were riding their horses through the field, the leaves were still green. (00:28:21 - 00:32:00)
Continuity mistake: When Colonel Ludlow and Susannah are eating dinner alone and hear the Decker's laughter from the room next door, they decide to join them. Susannah grabs her plate and her glass, and the Colonel his plate and the wine decanter. When entering the Decker's kitchen, there is nothing but their own utensils, plates and glasses on the table. If Pet brought more mugs and maybe also glasses to the table, she must have been very quick since it takes seven seconds from the last shot of her sitting at the table to Susannah starts pouring wine into a black mug, and gives it to Pet. Even if we only see Susannah pouring wine into one glass in addition to the mug, there are two kitchen glasses on the table filled with wine. When they raise their glasses there is no longer any glass at Pet's place, neither at Decker's. Pet must have given her glass away to the Colonel which doesn't make sense since he left his own almost full wine glass at the dining room. The amount of wine in the Colonel's new glass also varies from shot to shot measured by the decoration. (00:31:20)
Visible crew/equipment: When the British troops try to overrun the German lines soldiers are catapulted into the air by German grenades. At least once you get a good view of something like a springboard that was used for this purpose, that is when you hear Samuel's voice saying :"...the souls of those wounded so terribly...". (00:33:50)
Continuity mistake: During the war scene, when Samuel gets grazed by a bullet and Tristan covers him for protection, Samuel's hat falls off. The hat reappears, then disappears again. (00:35:57)
Continuity mistake: When Tristan and Samuel hug in the trenches in the war, at first Tristan's chin is on top of Samuel's hat, but when it cuts to the other angle, their heads are level, side by side. (00:36:00)
Continuity mistake: When the second German cavalryman attacks Tristan he is aiming his rifle at him. When he gets shot down he is holding on to the reins, and the rifle is gone. (00:39:40)
Visible crew/equipment: When Tristan pulls the third German cavalryman from his horse you see the face of Brad Pitt's double who, with his mustache, bears a strange resemblance with Adolf Hitler, something that can not at all be said about Brad Pitt. (00:39:45)
Plot hole: During the war sequence, when Samuel dies, how necessary was it for the two Germans to go through the trouble of setting up a machine gun to shoot him? I find it hard to believe they had no other weapon but that. It seems to have been done only to build suspense. (00:42:45)
Continuity mistake: When Samuel dies in the movie, if you watch closely there is blood running down his face in only every other shot. (00:43:37)
Continuity mistake: During Samuel's death where Tristan is cradling him in his arms, there is a stream of blood at the corner of Samuel's mouth. The camera cuts to Tristan's reaction, but when it cuts back to Samuel, the blood is gone. In later shots of Tristan preparing to remove his heart, the blood stream reappears. (00:44:00 - 00:44:55)
Revealing mistake: When Tristan takes revenge for his brother and scalps two German soldiers you can see that his knife just goes through the hair. (00:44:25)
Answer: Cutting locks of hair is often done in memory of the deceased. Knowing of her impending death, she cut two locks so as not to have them tainted by blood, but dropped one on the floor. I imagine it was the one for Alfred, but it is just my opinion.
I have goosebumps with this interpretation. I always thought that it was related someone with "scalping." She kills herself. She is her own victim. I don't know.