This is such a silly event, chapter 2 leon is pretty boring to do overall, let alone over and over again, her whole fight process gets on my nerves. probably not even going to bother after 2-3 kills they really need to be more creative with these events.
"I'm sorry squeeky, it's just a game, you got to get before you get got"
Thanks to the additional selections for chapters this is actually pretty easy you can get under ten minutes and if anyone can confirm it with a partner whenever either of you to finish her off it should count as two kills. Once it's done uploading and processing you can see just how fast you can do this fight:
Even so as Leon you don't want to rush the lowering of the mine cart the debre can and if you rush will put you into dying.
With this strategy you and a friend should be able to get 12 kills total in one hour.
I can understand why they can't expect as many kills for bosses as say the J'avo and Zombie Events but these should be pretty easy with enough players.
http://www.youtube.com/user/Starsoulklr I'm an Ultra Nerd for Video Games so see what I've got for viewing.