Joanie: I guess there's no such thing as safe sex with a werewolf.
Ellie: Why can't you just download porn like most normal teenagers?
Joanie: Putting on weight, Kyle?
Joanie: I'm not going to kill her. I'm just gonna rip her to shreds and let her choke on her own blood... and then maybe I'll eat her.





Answer: Different pieces of media have different rules and lore. Media isn't required to stick by classic rules, and this movie in particular toys with the classic rules a bit. For example, earlier in the film, Jimmy mentions that one of the ways to kill a werewolf is by severing the connection between the heart and brain, which would normally mean decapitation. However, blowing its brains out would also certainly accomplish that. Another example is the excellent werewolf movie "Ginger Snaps", in which pretty much anything can kill a werewolf as long as it inflicts enough damage.
TedStixon