Complex sentence: After the party, Peggy learns that Leslie has sold his old car, thus proving that he cares more about her than the car; she happily reunites with him, only to find he has bought an even older car.
Split into simpler sentences: After the party, Peggy learns that Leslie has sold his old car, thus proving that he cares more about her than the car. She happily reunites with him, only to find he has bought an even older car.