Complex sentence: She also had a guest appearance on "Tour of Duty" and "The A-Team", which was supposed to lead to her joining the cast; her "General Hospital" obligations prevented her from joining the team.
Split into simpler sentences: She also had a guest appearance on "Tour of Duty" and "The A-Team", which was supposed to lead to her joining the cast. Unfortunately, her "General Hospital" obligations prevented her from joining the team.