Hmm... the way I understood it, the Team Leader wanted Jiyoon to drop out of the wedding song thing because he could see that she was nervous about it. I haven't gotten the impression so far that he is jealous to the point of wanting to isolate her from her friends. It would be a terrible shame if that turns out to be the case.
We'll see. He isn't all that good at communicating, and she has misunderstood his intentions in the past, but it is certainly a thing that happens.
Maybe it's strange to call someone familiar team leader. But it's quite common in Asia? I would sometimes call team leader or something else instead of name.