The exact idea that captured both Linda Hamilton and James Cameron’s imaginations isn’t totally revealed just yet, but knowing that Terminator: Dark Fate is supposed to wipe the slate clean back to the end of Terminator 2: Judgement Day, we can kind of see what brought her back into the fold. Most importantly, the fact that Sarah Connor’s alleged death after a battle of cancer, as noted in Terminator 3: Rise of the Machines, is now erased.
Article source: https://www.cinemablend.com/news/2470103/linda-hamilton-confirms-james-cameron-convinced-her-to-return-for-terminator-dark-fate