Complex sentence: Boucher was asked to write two endings to "Face", one where Leela left with the Doctor and one where she stayed behind, and the decision to have Leela become a companion was made soon after.
Split into simpler sentences: Boucher was asked to write two endings to "Face", one in which Leela left with the Doctor, and one in which she stayed behind. The decision to have Leela become a companion was made soon after.