Complex sentence: Katie agreed, deciding to give Perdy custody, telling Jonny but not Perdy about her decision as she worried that Perdy would say tell Grayson but Paul made Grayson suspicious about what Katie was up to.
Split into simpler sentences: Katie agreed, deciding to give Perdy custody, telling Jonny but not Perdy about her decision. She was worried that Perdy would say something to Grayson but Paul made Grayson suspicious about what Katie was up to.