About a detective vampire or something or other who stops a girl werewolf from committing murder, she gets mad that he stops her. Her father or something or other is leader of the werewolves and there's a big political problem. The two run into a pair of werewolves that are supposedly cousins, but they found out they're having sex and they're really teenage runaways. In the end the vampire and werewolf have a kid I think.

You might check out Angela Knight's Mageverse series - it's vampires and werewolves, I know, and at least a couple of them are cops. I've just gotten my first book of hers and haven't read it yet, so can't give any more detail. There are a _lot_ of urban fantasy books out these days, though.

(touchstone not working - here's her author page)

I do not believe that is it.

Blood Trail by Tanya Huff? Henry Fitzroy (several hundred year old vampire) gets involved in investigating a werewolf-related case. (Makes a change from chasing demons, ghosts, and/or other vampires...)

MaryJanice Davidson perhaps?

Kelley Armstrong maybe? Definitely werewolf politics going on in her series. Though I can't remember if vampires are involved.....

How about Patricia Briggs - the Alpha and Omega series. The first Book is Cry Wolf and the 2nd is Hunting Ground. I don't know if this helps.

nope, none of the above... my heart skipped a beat when Tanya Huff was mentioned, I was going through my dad's book collection and he has a few of her novels... but alas that was not it.

Maybe Full Moon by Jim Butcher (Dresden Files series)?

P.N. Elrod's lengthy Vampire Files series (first book is Bloodlist) has a vampire detective protagonist. Maybe one of the books has a werewolf subplot?

The OP also reminded me of the teen werewolf story, Blood and Chocolate, which has the elements of preventing the teenaged female werewolf from committing murder, her parents being the leaders of the werewolf community, an issue with cousins, and her choosing a mate by the end of the book. There were absolutely no vampires in it, although the author did write a teen book specifically about vampires, The Silver Kiss.

nope, thanks for the suggestions though

Might be kind of out there, but maybe Lonely Werewolf Girl?