In my online game, it's often hard for me to handle NPCs with the loads of characters we have so sometimes I ask or a player volunteers to play some of them. The issue is though, that one player (let's caller her player A) has taken it upon herself to take two NPCs that she provided for my use so she could rp relationships with the PCs of players B and C.
When I asked the player about this, she had said that 1) She did it to provide more rp opportunities to the players and that 2) I should be happy I created a world they want to rp in more than once a week. I can agree with this to a degree as player B just treats it as another event to play with but player C has a hard time engaging in the plotline. When it comes his time to act he says "umm uhhh" and ends up doing what others tell him to.
I'm worried that player C is only engaged in the plotline as far as his reactions to player A. Because he responds with banter back and forth with A frequently, and it varies with his interactions to the other players. I worry that player A occupying player C with an NPC is preventing such interactions from happening.
So, how do I handle this and prevent it in the future?
Edit: In short, Player A is distracting Player C by playing an NPC.
(Sorry about the mistaken edit. Pffbt. Writing questions while sick man...)