Complex sentence: Karen discovers the necklace in Harry's coat pocket and assumes it is a gift for her; when he gives her a music CD instead, she intuits that the more glamorous gift was for Mia, and confronts Harry.
Split into simpler sentences: Karen discovers the necklace in Harry's coat pocket and assumes it is a gift for her. When he gives her a music CD instead, she intuits that the more glamorous gift was for Mia, and confronts Harry.