If she loves being with the terminally dull Paul so much, why doesn't she just tell Matt it's all over, ask him to leave and install Paul in Ambridge? It's her house, isn't it?
She's not tied to Matt through kids or financial necessity, and she doesn't seem to like him very much even when he's trying to be nice to her.
Is it just the thought of Peggy's cat's bum face that's stopping her?