She is a cat, not a vampire-slayer. That is to say, she does not appear to have the necessary physique to be very effective in the capacity of vampire-slayer. Having said that though, I have not seen any vampires in the immediate vicinity, so she may indeed be very effective in this capacity. Conversely, the lack of vampires may just be a coincidence.
Regardless, of her ability (or lack there of) to battle the vamps, she requires looking after, as her owners are travelling around the world in 80 days, and they, rather misguidedly, have left her and their house, in my somewhat trustworthy and responsible hands.
Buffy is a bit noisy at times, but she' s a bit cute and very affectionate, and she comes with a superb house in the Sydney suburb of Summer Hill, and a semi-naked guy.