Vampire book that I can not remember the name of! HELP!?

Ok, so I distinctly remember reading a fictional book that contained vampires and now can not remember most of the storyline or characters names. In the book there is a woman who for some reason is living with a female vampire. The main character keeps making stupid mistakes that attract the vamp so the vamp gives her a book on how to attract vampires (to be used in the opposite manner of course.) At some point during the book she is turned into a rodent of some type (or a mink or maybe a ferret) by the big bad guy. She is put into a fight with a rat, who turns out to also be a human and the two end up escaping with a little help from the vampire and some guy if I remember correctly Please help me remember what book this is...as it is starting to get on my nerves that I can not remember.