Maybe nothing. Since the finale took place years in the future, Una could've been imprisoned for some other event that may still happen in the prime timeline.
This is the logical answer, but I don't like it, since the writer's intent was to foreshadow her arrest at the end of the episode. This really can only be something that Pike does differently after experiencing the events of the finale, but I can't think of anything that should have affected the trial's outcome.