Enough Firearms and Dex, plus silver bullets, will give any werewolf pause. Particularly if the vamp knows what's coming.
The problem isn't so much that werewolves just tear vampires apart in melee. That's part of it, definitely. It's also that werewolves can and usually do attack during the day. And in packs. A well-prepared vampire with the right resources and preparation can take on a single werewolf. It'll be chancy, but it can be done. The problem is that then said vamp has to deal with the rest of the pack.
So sure, Nines could have gotten the pup to play fetch with a grenade, or gone full Bonny & Clide on its ass with silver bullets. You don't need disciplines to do it, and Ventrue have one of the most useful for fighting against a Garou to begin with: Fortitude. Using the Revised rules (the ones from Bloodlines 1), it's the easiest way to soak aggravated damage. And anything helps when you're going up against something that gains +4 Strength and aggravated damage in Crinos.