Petulia is a young witch who was apprenticed to Goodie Gwinifer "Old Mother" Blackcap. By the events of Wintersmith Petulia has gained considerable respect in the Ramtops for her abilities with animals, particularly with pigs and, as a result, gains the nick-name "the pig witch", a name she doesn't appreciate much when coming from Annagramma Hawkin - too much pig and not enough witch is her assessment. Her talent wins her the Witch Trials in A Hat Full of Sky, when she performs the pig trick using only a sausage instead of a live animal. What this trick actually is is not revealed. She is part of the network of peers gathered by Annagramma Hawkin who form a coven and is a friend of Tiffany Aching. When with the coven, she has a tendency to mumble, stutter, and be extremely deferential which leads to her being bullied by Annagramma. Generally a kind soul who is thoughtful of others' feelings, she gains new strength by the end of A Hat Full of Sky becoming self-confident and secure. Despite her disagreements with Annagramma, she agreed to show her a few useful tips on dealing with livestock when Tiffany asked her to. By I Shall Wear Midnight, her skill with witchcraft and pigs appears to have found her a husband, Matty Weaver, the sort of stolid Lancre pig-farmer who values a woman's ability to tuck a pig under each arm, treat their ailments, and make their transition to pork roasts and bacon a humane one. She appears to actively court him; showing up regularly to treat his pigs for everything from 'blind heaves, brass neck, floating teeth, scribbling eyeball, grunge, the smarts, the twisting crews, swivelling and gone knees" - diseases, more than half of which are not normally found in pigs at all and one is "a disease known only to freshwater fish". Petulia is an expert at Pig-Boring, which is the most humane way of slaughtering an animal. She simply chooses her animal, and then talks to it in a most earnest monotone voice about trivial things of parochial importance until its eyes close and it slumps to one side, having by then given up the will to live.
Petulia is also, apparently, acuphobic, the fear of pins - an interesting phobia for a witch who might be expected to stick pins in wax dolls or as a pig farmer's wife and veterinarian, be expected to give injections to the pigs.
She is named after Petulia, the goddess of negotiable affection and the patron of the Seamstresses Union - a rather unfortunate name choice on the part of her parents. However the oversight is understandable given the fact that there are over 3000 gods and goddesses so keeping track of them is nearly impossible.