Kiri'zhu would be fun to put with her I think. That would be a terrifying duo to be put up against! If people thought it was bad having one or the other hunting them, imagine if they were working together!
I don't really see Kira having a reason to work against the vampire, seeing as she is only an assassin and not a demon/vampire hunter. She really only takes missions to assassinate other humans. However, if you did want to try and find something for them, I'm open to ideas. Personally, I just feel Kiri'zhu would work better.