I actually find it pretty believable that two 18-year-olds who have seen a photo of a girl apparently dead on a spot and find a dead body buried on that same spot assume that the body belongs to the girl in the photo. Even more believable because one of them is emotionally attached to her and there hasn't been a missing person in tons of time. Now, Nathan and Jefferson may have taken a bunch of dead birds, bury them and put Rachel's clothes on top, hence the smell and the assumption, who knows at this point, but the doe fading.....I do think it's Rachel's body.
Yeah, and the way the scene played out with the music, etc, leads me to mostly believe that she is actually dead. But, I still thought it was weird we never really see her, just the reactions from Chloe and Max