The follower should pivot at the beginning of a step.
If you automatically pivot at the end of a step, you are presuming to know the next direction. Finish your step, stretch onto your new base leg, and look to perceive the next direction. (There may not be one yet! – Thank you Armin!)
Note that the follower is responsible to (1) get her hips rectalinear to the direction the leader has indicated. (2) make sure her foot is in relative to her hips. (See diagrams below.)
Once the leader has indicated the next direction, if it requires a pivot to make your hips rectalinear to the direction and to get your foot in relative to the direction, use the power coming from the leader’s intention to pivot just prior to your projection, as part of the initiation of the step.
If the pivot is less than 90 degrees, the leader won’t have to give you extra power. If he is asking you to make a large pivot he will deliver power and time to you to help you.