Complex sentence: Chrissy is the leader of the trio being the smartest and the oldest (she is 18-years-old while the other two are 16) and is also the manager of the Khaki Barn and Nikki's boss.
Split into simpler sentences: Chrissy is the leader of the trio (being 18-years-old while the other two are 16). She is also the manager of the Khaki Barn and Nikki's boss.