Complex sentence: She first confided in Bess of Hardwick, who however refused to listen to Catherine and berated her for implicating her, and then in her brother-in-law, Robert Dudley.
Split into simpler sentences: She first confided in Bess of Hardwick, who refused to listen to Catherine and berated her for implicating her. Catherine then went to her brother-in-law, Robert Dudley.