I actually stumbled upon the answer to this by accident. Shane Black is filming Ironman 3 here in Wilmington at the moment and I wanted to show the girlfriend just how awesome the combination of Shane Black/Robert Downey Jr can be. I bought Kiss Kiss Bang Bang on blu-ray, and guess what? It's the film you are looking for.
In the beginning, Harry (the main character) is at a party in Hollywood. He is approached by a blonde chick who says that she is an actress. It then cuts to the scene you have posted here. It's only a 10 second little clip, and it's funny as hell. Sorry to disappoint and let you know that it is not from a feature length horror film or anything.
Further proof from google image search for "Kiss Kiss Bang Bang Werewolf":
Hope this helps!
(I posted without looking. Damnit! Thor beat me to it by a good while. Here I was thinking I was smart.)