You know that person you are struggling with? How do you know they are not fulfilling their purpose? How do you know they are not doing exactly what they came here to do? Is it because what they are doing doesn’t fit into your map of the world?
Maybe what they are doing is exactly the experience they agreed to give you so that you could learn what you need to about yourself. When we believe that someone should be doing something differently, it’s not because they should, it’s because there is something we are learning from it. Maybe we need to change a belief within our self and they are showing us what that belief is. What are you learning from that person you are struggling with?