One of my middle school students wrote me an email explaining that a member of her team would not take the role of secretary to take notes for her group. Here was my response:
Thank you so much for the wonderful job you have been doing leading your team for our play. I am pleased with your leadership and proud of your developing skills.
As a leader, sometimes other people are difficult to deal with. Sometimes they can't do the jobs we want them to, and sometimes they can but choose not to.
If one of your teammates will not complete a certain job despite repeated requests, I suggest you ask her which role she would like to take, and if it is reasonable, then let her take that role instead. All people are not good at all things, and I expect you will feel better and find more success if you allow you team to build on its strengths rather than focus all of your attentions on its weaknesses.
Thank you, again, for all of your work.