The eldest Daughter of the four Villiers siblings. The family history standing and image were more important to her than anything. She continually nagged her brother Ferdy to leave off his magic career, calling it childish, and get a 'proper' job. Now she does the same with her nephew, Howard, who shares Ferdy's passion for magic and for which Jennifer keeps belittling him.
She has also always refused, against siblings' opinion, to sell their lates parents' house, despite it being too much expensive for all of them to handle.
When a woman called Claire came to apply as Ferdy's stage assistant, Jennifer immediately sent her away, telling her there was no position. When Ferdy not only hired her, but became engaged to her, Jennifer was furious and hired private detectives to dig up dirt on her. When a record for minor theft and drug use was found, Jennifer forced her elderly aunt, who actually liked Claire, to report a valuable art-deco statuette she'd entrusted to Claire for a valuation, as stolen. These actions led Ferdy to committ suicide, followed shortly by Claire too, but Jennifer never admitted that this tragedy was mostly her fault.
Her actions were recorded by Aunt Lydia as 'evil' in the privacy of her diary.
Nine years after these events, she was targeted as an object of revenge.
The four siblings reunite for Chrismast and, at the Christmas dinner, Howard opens a Christmas cracker containing a threat. At first she accuses him to have written the threat for fun and then blames him when Lydia has an accident in the garage. Then Lydia falls down the stairs, but Jennifer refuses again to admit that there is something strange, blaming this time her aunt's old age. When DCI Tom Barnaby and DS Dan Scott arrive to investigate, she tries to minimize the situation, still blaming Howard's supposed prank when he speaks to the detectives about the garage's accident and Ferdy's suicide.
After some researches, the two officers discover that Lydia had written diaries. Even though the diary of the year of Ferdy's death isn't found, thanks to the diary of the last year the family realises that Jennifer is actually hiding something. In response to their questions, she keeps refusing to admit what she has done, blaming now Lydia's sanity, in spite of the fact that by then its clear how all these excuses have destroyed her trustworthiness. When her brother Ross points out how obvious is her fear, Jennifer decides to prove he's wrong by going to a hunt where DCI Tom Barnaby strongly advised her against going.
Her shotgun shells were tampered with and led to a misfire. After she reloaded, one barrel was double loaded and it exploded in her face, killing her.
After her death, Dominic Jones, her killer and Claire's brother, gives back the stolen diary to allow the rest of the family to know the truth. At first Aidan tries to get rid of the diary out of fear of what's written there, but Ross prevents it and reads it aloud, allowing the rest of the family to discover what kind self-centered liar was Jennifer.