By the time the story-line has caught to The Sims 2, Diane and her husband Jeff are already deceased. Her son, marriedMary-Sue Pleasant (néeOldie), and fathered two children, Angela and Lilith. Her daughter married John Burb, and had one child, Lucy Burb. She can be seen in Daniel, Angela, Lilith, Jennifer and Lucy's family trees. Both she and Jeff died around the time Angela and Lilith were toddlers and Jennifer was pregnant with Lucy. It's unknown if she died before or after her husband Jeff, as Daniel's memories indicates that Jeff died first, while Jennifer's memories indicates that Diane died first.
Diane cannot become playable without the use of hacks like SimPE. However, her facial features are highly customized (using the second face template as a base), so regenerating her with SimPE is a very difficult task. According to her SimDNA in SimPE, Diane's hair was red before it turned grey. However, neither of her parents had red hair, and her hair was brown in The Sims. This could imply she may have dyed her hair brown in The Sims, but it could also simply be a continuity error. According to her age data, Diane had 36 days left in the elderlife stage when she died. Oddly, both Hula Zombie and the Grim Reaper are ticked as "known", with unique relationship scores when inspecting her relationship data.
This Sim has no character data and cannot be resurrected in-game. For more information, read this guide.