Complex sentence: However, Sadie tricked Rosemary into thinking the marriage had been consummated so they agreed that in exchange for the Sinclair business most valued by Rosemary, Sadie would get the marriage annulled.
Split into simpler sentences: However, Sadie tricked Rosemary into thinking the marriage had been consummated. Rosemary and Sadie made a deal: in exchange for the Sinclair business most valued by Rosemary, Sadie would get the marriage annulled.