Years ago I read an article about Mrs. Bennet in Pride and Prejudice in which the author made the point that while Mrs. B. may be foolish, she is also correct. Her daughters will be in dire straits without husbands to provide support.
I think this is why Pride and Prejudice and Zombies works as well as it does. Finding husbands is a life-and-death proposition for the Bennet daughters. Bringing in zombies is just a higher degree of risk. Little Women and Werewolves, on the other hand, wasn't as good a mash-up. The March daughters' response to the werewolves in the story doesn't make sense in the context of Little Women world.
I'm going on about this, because there was a discussion on my Facebook wall today about an article at The Literary Hub called Jane Austen's Most Widely Mocked Character Is Also Her Most Subversive by Rachel Dunphy. It's very intriguing, putting a feminist spin on Mrs. Bennet.
I like it, but I suspect Jane Austen wouldn't have a clue what Dunphy's talking about.