The fierce warrior Lady Catherine de Bourgh has killed more zombies than any woman in England. That's a pretty big deal, and it's why Elizabeth is so psyched to meet her when she visits Rosings Park:
Elizabeth's courage did not fail her, even though she had been regaled with stories of Lady Catherine's accomplishments from the time she had been old enough to hold her first dagger. The mere stateliness of money or rank she could witness without trepidation, but the presence of a woman who had slain ninety dreadfuls with nothing more than a rain-soaked envelope was an intimidating prospect indeed. (29.8)
Unfortunately, Elizabeth figures out pretty quickly that Lady Catherine is all bark and no bite.
Like her original inspiration, this formerly great warrior just goes on and on and sticks her nose into everyone's business. She's also got some really snobby ideas about where exactly a lady should train to fight zombies—Japan, never China. Elizabeth fights her ladyship's ninjas but rarely sees Lady Catherine actually lift a finger or demonstrate any actual skill. Not so impressive now, is she?
The battle royale between these two femmes fatales comes when Lady Catherine shows up at Longbourn to try to stop Elizabeth from marrying Mr. Darcy:
"Will you promise me, never to enter into such an engagement?"
"I would sooner die than see my honour so defiled."
"Then Miss Bennet," said Lady Catherine, setting down her parasol and removing her coat, "die you shall." Upon this, she set her feet for combat. (56.54-56)
Elizabeth wins the fight and lets Lady Catherine live—and in the process, snags herself a man. It's this act of mercy that makes Mr. Darcy realize Elizabeth has real feelings for him, and after that he's hooked.
Crud. That is exactly the opposite of what her ladyship had in mind. Oh, well. She always has her ninjas to keep her warm at night.