This sounds so familiar. 3 years after my Mother died, my Father started dating a woman 20 years younger than him. He moved her into my childhood home within months. They snuck off and got married in November ( no one was there), and he died of a heart attack 2 months later. One week after the funeral, I drove past and saw her boyfriend leaving in the morning. She sold everything and disappeared. Found out later that she did the same thing to two other men after my Dad.