Sandy raised two daughters, JJ and Rosaline, with her husband. When she was seventeen years old, Rosaline committed suicide, leaving the entire family distraught, especially Sandy since she and her husband chose to ignore the warning signs of Rosaline's depression. Eventually, the Jareau family moved on from the tragedy. Sometime prior to the start of the series, Sandy became a widow when her husband died of unknown causes. She was mentioned in Zoe's Reprise, where it is stated she had created a whole album full of photos of her grandson Henry.
In Run, Rossi calls her over to attend to her daughter's wedding with Will, loaning her her beloved wedding gown, which fits onto her with ease. Sandy walks JJ down the aisle during the wedding and then watches in pride as JJ and Will get married. Sandy later participates in the wedding dance and toasts to the happy couple.
In If the Shoe Fits, she comes to visit JJ and Henry for a couple of days. While she and Henry go over a set of childhood photos of JJ, which she planned to convert online, Henry spots a photo of a younger JJ with Rosaline, who he asks about. Sandy gives him an honest answer and innocently tells him that Rosaline is in a better place, explaining why he hasn't seen her. When JJ finds out from Henry about it, she confronts Sandy about it, telling her about her and Will's plan to tell Henry about Rosaline when he was older. The two have an argument, during which Sandy warns JJ about what she and her husband had done to ignore Rosaline's depression. Their argument is cut short when JJ is called over to the BAU headquarters to have a team meeting concerning a case. Off-screen, Sandy returns back to her hometown.