In the Melody Lane bar, Jennifer returns with a tray of the two "9-11" drinks. She says, "Tower 1 isn't full enough." The camera cuts away and when it cuts back "Tower 1" is more full (blue layer). The camera cuts away again, and when cutting back, "Tower 1" is back to it's previous lower level.
Needy does research on the occult and determines that Jennifer is a succubus, a demon which feeds on flesh. A succubus is believed to be a female demon that has intercourse with sleeping men, and does not, in fact, eat flesh.
Before Jennifer is stabbed, the right strap of Needy's dress is off her shoulder and damaged, while the left is intact and in place. When we see Needy's reaction, the straps are off both her shoulders. When Jennifer removes the pole and walks past Needy, the strap is back in place.
Jennifer is killed by a utility knife with a snap-off blade that isn't thick, strong, or sharp enough to penetrate the rib cage. In real life it would cause some damage, but it would snap when it hit bone.
When Jennifer kills Jonas in the woods, a deer eats Jonas' remains in one shot. Deer don't eat meat. However, this may have been deliberate to show the effect that Jennifer has on the various animals. They don't tend to silently gather to watch murders in the woods either