Diana was once a professor of archaeology and married Edward, a witch. However, their marriage deteriorated and the two divorced when Sabrina was ten years old. Due to The Witches Council's decree (hoping to discourage mortal-witch marriages), Diana can not see her daughter without being turned into a ball of wax.
Originally, the rule only lasted for two years after Sabrina turned sixteen and learned that she was a witch. Once Sabrina turned seventeen, the rule changed and the decree lasted only until Sabrina received her Witch's License. However, on Mother's Day, Sabrina broke the rules by magically sending a letter to her mom in Peru, being told that she now had to choose between keeping her magic or seeing her mother ever again. Sabrina chose her mom and got sent to visit her. Sabrina and Diana had a nice reunion in Peru where Diana gave her daughter advice on her love life and sent her on her way back to Westbridge.
Back at home, Sabrina discovers that her choice was simply another test and she got her magic back. Unfortunately, she cannot see her mother, face to face, ever again without the latter becoming a ball of wax.
Three years later, Sabrina, upon feeling like she's being watched, sneaks up on her stalker to discover that it's her mother. Diana tells Sabrina that every year, she sneaks to town and checks up on her, making sure to stay out of sight so that they do not see each other face to face. However, they accidentally lock eyes and Diana gets turned into a ball of wax. Sabrina and her aunts try to appeal to the new Witches Council to turn her back but they cannot overturn the old Council's decree. Sabrina and her mom try to go on with their lives and spend quality time together but it ends in tragedy when Sabrina accidentally leaves Diana by a hot iron and she melts. Devastated, Sabrina starts to cry and her tears drop into the melted wax and gives Diana her human form back. Hilda and Zelda quickly turn the two away from each other, letting them know that if they ever look each other in the face again, there is no way to ever turn her back.
On Sabrina's wedding day, Hilda and Zelda plead to the Witches Council to allow Diana to go to the wedding without consequences. Hilda then volunteers Zelda as a sacrifice and the Council turns her into a candle in exchange for Diana being allowed to see Sabrina. When Sabrina questions her love for Aaron after discovering that their soul stones don't fit together, Diana encourages her daughter to stop using magic and start listening to her heart. Sabrina ultimately chooses to leave Aaron at the altar and run off with her high school sweetheart Harvey, during which Diana looks on with Edward and the rest of Sabrina's family and friends saying "it's about time."
- Coincidentally, Diana's ex-husband, Edward Spellman, is also played by two different actors.
- For some reason, the rule changed after the Season 2 episode "Mom vs. Magic;" originally, Sabrina only had to wait two years (or until she passed all of her Witch's License tests) to see her mother again. The rule later became that the two can never see each other.
- In the early Sabrina comics and the pilot movie, Diana was a witch. In the movie, it was explained that when a witch turns sixteen, she has to be handed over to magical trainers which is why Sabrina is not allowed to live with her parents. Diana and Edward move back to the World of the Witches until Sabrina completes her training with Hilda and Zelda.
- Sabrina's fiancee Aaron Jacobs refers to Diana as "Mrs. Spellman" in "Soul Mates," indicating that she kept the last name after the divorce or he may not have known her maiden name, having never met her before.