To ensure Ron gets the peaceful, happy life he desperately deserves, she lets him erase his memories of her and their entire relationship.
"Appleton" stands out as a high-water mark for the series. It proved that a show built on absurd conspiracy theories—like reptilian elites and flat-earth plots—could deliver an incredibly grounded, mature exploration of identity and love. [S2E8] Appleton
Reagan comes to the crushing conclusion that if she stays with Ron, one of them will inevitably end up miserable. To ensure Ron gets the peaceful, happy life