Complex sentence: Ann Jillian, who was then a teenager, was also added to the cast as Millie Ballard, Steve Baxter's receptionist, who later went on to star in her own series, "It's a Living" and numerous television movies.
Split into simpler sentences: Ann Jillian, who was then a teenager, was also added to the cast as Millie Ballard, Steve Baxter's receptionist. Jillian went on to star in her own series, "It's a Living", and numerous television movies.