Jasmine Thomas is Ashley Thomas's niece. During her time in Emmerdale, aspiring journalist Jasmine embarked on a relationship with Debbie Dingle. She killed boyfriend Shane Doyle after he attacked Debbie so she was sent to prison.
Jasmine is later suspended from school and returns to the village. She helps her grandfather Sandy settle in and she becomes close to him. Jasmine and Ashley's wife, Laurel, help Sandy and Ashley bond. After briefly returning to school, Jasmine is expelled but gets a place at the local college so she can take her A Levels.
Debbie kisses Jasmine to get a reaction from her father, Cain, but both girls realise their feelings for each other are stronger than friendship and start dating. Jasmine, however, is caught in the fight between Cain and Debbie as Cain seduces her. Jasmine sleeps with Cain but discovers he used her to get at Debbie after she catches them together and is devastated. She soon reconciles with Debbie and realises she is pregnant. Debbie tells Cain and also that Jasmine plans to have an abortion, which she does, paid for Sadie King. Cain is devastated as he wanted her to have the baby and Debbie gleefully tells him that Sadie was involved too.
Jasmine finds a job as a journalist and begins investigating Tom King's murder. Jasmine discovers Jamie Hope lied about his whereabouts at the time of Tom's death and wonders if he was responsible but helps him prove his innocence.
Jasmine begins dating David Metcalfe, but they break up when David tells her that his father, Eric Pollard, is trying to cheat Pearl Ladderbanks out of some money. Jasmine tells Pearl what is happening and gives her a car that David bought for her. Jasmine and David reconcile briefly but split again when he has an affair with Nicola De Souza. Jasmine gets revenge on Nicola by exposing her lies about her husband, Donald De Souza, in the local paper and making sure his son, Miles, reconciles with his father and stops drinking again. They realise their feelings for each other and start dating but Jasmine ends it when he gets jealous that she is friends with Jake Doland. Jake and Jasmine start dating, despite tension between their families over the baby swap of Daniel and Arthur.
Jasmine decides to write a story about a local criminal family; the McFarlanes. Using Debbie's contacts, she meets policeman Shane Doyle at The Woolpack. Shane later goes to Jake's house, claiming there have been complaints about the noise, and winds Jake up so much that Jake attacks him. Shane promptly arrests him for being drunk and disorderly while Jasmine dumps him for thinking that she'd cheat on him. Shane makes his personal interest clear but Jasmine is not interested until she learns Shane has arrested Danielle Hutch, a girl with ties to the McFarlanes. Debbie warns Jasmine to stay away from Shane, but she refuses to listen. Shane tells Jasmine that he let Danielle go because he felt sorry for her and they sleep together.
When Jasmine questions Shane further, he almost becomes violent so she searches his flat and finds large amounts of cash. Unfortunately he finds her hiding in a wardrobe and boasts about his illegal activities. Jasmine pretends to understand his reasons before trying to escape but Shane catches her and tries to rape her. Debbie arrives and hits Shane on the head with a chair leg, knocking him out briefly, but he comes round and grabs Debbie. Jasmine picks up the chair leg and hits Shane again, killing him this time. Debbie, Eli Dingle and Jasmine wrap Shane's body up and dump it in a lake at Home Farm.
Jasmine buys a plane ticket online using Shane's credit card, as he had some time off work but starts having nightmares. Shane's body is found by Victoria Sugden after she falls into the lake. Debbie and Eli try to keep Jasmine calm before the police question her. Laurel, however, notices how jumpy Jasmine has become and asks if she is pregnant, making her laugh hysterically before admitting to Laurel that she killed Shane so Laurel tells her that she must go the police. Jasmine agrees but on hearing of Ross Kirk's arrest and that he has been charged with Shane's murder, Debbie and Eli persuade her to keep quiet but Jasmine's conscience gets the better of her and she tells Debbie that she wants to go to the police and confess.
Calling her bluff, Debbie packs a bag and drives Jasmine to the police station. While there, the girls have a heart to heart and they kiss again and start dating again. However, Ross is cleared and Eli is arrested for Shane's murder, so Debbie and Jasmine decide to go on the run. Debbie takes a taxi and Jasmine catches a bus to meet her but Debbie is arrested so Jasmine leaves alone. She visits her grandfather in Scotland but returns and bursts into a court hearing for Debbie and admits killing Shane.
After being questioned by the police, she is charged with manslaughter. Jasmine pleads guilty and is sentenced to four years in prison. Debbie visits and Jasmine tells her she does not want to see her any more because she needs to fit in. The two girls say goodbye and Jasmine explains that their love will last forever. She is then led back to her cell.
Jasmine would have been released in 2013, but it was not mentioned by anybody. She also did not attend Ashleys' funeral, so it is possible she had not heard about his death (or got back in touch at all since leaving prison)