Complex sentence: It was evident that she and Josh were old friends--they had attended Yale Law School at the same time, where she dated his roommate--and their flirtation, and subsequent relationship, took up much of the storyline in season three.
Split into simpler sentences: It was evident that she and Josh were old friends, as they had attended Yale Law School at the same time, where she dated his roommate. Their flirtation, and subsequent relationship, took up much of the storyline in season three.