Lydia might be the youngest Bennet daughter, but she's definitely determined not to be left behind. She can slay a zombie with the best of them, of course, but that's not her biggest accomplishment:
"Oh!" said Lydia stoutly, "I am not afraid; for though I am the youngest, I'm also the most proficient in the art of tempting the other sex." (2.17)
That must be one of those elective classes you can take when you major in zombie slaying. Interesting.
Basically, Lydia just as immature and silly and vain as her Austen counterpart, but, in this story, she can kill a zombie with the flick of her dagger, as well. Too bad she's more worried about flirting with officers than defending England from the undead plague…
When she finally falls for Mr. Wickham, Lydia isn't sorry in the slightest. In fact, she comes back to Longbourn proud as a peacock. Here she is telling Elizabeth about her wedding:
"We were married, you know, at St. Clement's, because it had the fewest steps to carry my beloved up[…] And there was my aunt, all the time I was dressing, preaching and talking away just as if she was reading a sermon.
However, I did not hear above one word in ten, for I was thinking, you may suppose, of my dear Wickham. I longed to know whether he would be married in his blue coat, or if he had soiled it like the others." (51.21)
You've gotta hand it to the girl—she has no sense of shame. And she has no fear of the life that's in front of her, which will include perpetually caring for a husband who's been wounded so badly that he just poops all over himself all the time. She's not terrified of the walking dead, and she's not afraid of this, either.
But that's Lydia. She just gives zero cares. Hey, we sort of even love her for it.