As far as we know, every Diane in the CFC was either abandoned by her husband or was murdered when he actually chose to stay. The ones who lived raised their daughter alone, occasionally having him return, each time hurting her more and making Beth idolise him more when he inevitably left again. Beth would never understand Diane until it was too late, until every version of her mother had been erased from existence.
Every Diane was erased at the whim of one man in an infinite sea of Ricks. How many Dianes never even met Rick - maybe never even had a Rick in their dimension?
Even after she was torn from the fabric of infinity, Ricks tried to fill the hole left behind, even the one who took her away. They built robots and AIs with her likeness, her voice, her personality. They used her as servants, as punishment, as motivation.
Rick C-137 made one such AI to serve as all three. He chose to fester in his grief, and he brought her back from the dead to share his suffering. He left her, chained to the site of her daughter's death, of her own death, endlessly searching for their murderer. He left her for years at a time, while he went out on revenge missions and had fun and tried to move on. He left her there with nothing more than the decaying shells of their former neighbours and acquantainces, who could never remember or understand their situation. Did she try to reach out to them? Did she try and get them to help? Is there even a way she can be helped?
The only way for her to spend her time was in a futile attempt to fulfil her purpose: an impossible search for her and her daughter's killer.
Finally, after so long, Rick returns. He doesn't want to know about the one thing he created her to do, about the one way she's had to occupy herself all this time. He didn't even mean to return. He gets to move on with another version of his family, and that's all he cares about.
He finally manages to move on, releasing the souls he's kept trapped in time.
This time, she truly is alone.
