Character mistake: At the scene at the dinner table where Pat and Tiffany meet, the prescription drug "Trazadone" is mispronounced with a long A as in "trayzadone." This a fairly common drug used for depression and as a sleep aid. Any nurse or pharmacist could tell you the correct pronunciation. Interestingly, the other lesser known drugs were pronounced correctly.
Character mistake: In the scene where Carlisle returns with Alistair he asks Edward how many vampires showed up, Edward replies 18. At that point there were only 16. Vladimir and Stefan arrive a few scenes later and are part of the group assembled for battle that totals 18 of the witness vampires.