Complex sentence: Miriam also tells Drew that back in 1927 she saw Jewel murder her husband, and she's been using this knowledge to blackmail Jewel for all these years, while plotting to gain possession of Charlotte's wealth.
Split into simpler sentences: Miriam also tells Drew that back in 1927 she saw Jewel murder her husband. She's been using this knowledge to blackmail Jewel for all these years, while plotting to gain possession of Charlotte's wealth.