Diane 'Dee Dee' is Bernice Blackstock's youngest daughter.
After months of bed rest, Bernice gave birth to her second daughter on 21st September 2004, the day her mother Diane married Jack Sugden. The newlyweds immediately rushed down to Brighton to visit Bernice and the 8lb 4oz tot, whom Bernice and her partner Charlie named Diane after Bernice's mother.
By 2012, Bernice and Charlie's relationship had ended and Bernice left Charlie and Dee Dee and returned to Emmerdale. Diane visited Charlie and helped him with Dee Dee whilst he came to terms with the breakdown of his marriage. Bernice hoped that Dee Dee would move in with her and her new partner Steve Harland, but Charlie decided to move to Australia with Dee Dee instead. In September 2015 Bernice and her partner Lawrence White visited Dee Dee. In April 2017, Bernice and Gabby visited Dee Dee.
In November 2017, Dee Dee arrives unannounced in Emmerdale and reunites with Bernice, Gabby and Diane. Bernice and Gabby admit to Diane they exaggerated their life to make it seem glamorous to Dee Dee.
Dee Dee meets her aunt, Nicola King, and Nicola encourages Bernice to keep money from a betting slip from one of Bernice's clients who recently died and was Lydia Hart's distant cousin in order to keep up the pretence she is rich. Bernice rents a Bentley from Debbie Dingle and buys gifts for Dee Dee and Gabby. Diane suggests Bernice admits the truth when Dee Dee says she enjoys spending time with Bernice. Bernice contemplates telling the truth until Dee Dee announces Charlie gave her permission to stay for Christmas. When Dee Dee and Bernice return from a holiday, she comes clean to Dee Dee that she is not rich and the money is Lydia's inheritance. Lydia is initially furious when Dee Dee lets slip about the inheritance and Dee Dee insists they return everything they bought. Dee Dee tells Bernice that she is returning to Charlie as he wants her home.
In November 2019, Dee Dee returned to the village for her mother's wedding to Liam Cavanagh and made Bernice overjoyed when she revealed her plans to go to school close to the village so they could see each other more often. However, the day before the wedding, Dee Dee got a phone call disclosing that Charlie was in hospital after a horrible car accident. With no certainty that he would ever fully recover, Dee Dee returned to Australia and Bernice came with to support her.