Revealing mistake: When Tristan kill the guy in the liquor storage and the hay fork goes through his chest, you can see that parts of the hay fork's tines closest to his body are not covered with blood. (01:51:05)
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)
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.
I agree, I always thought it was a symbolic scalping.