My U11s have the same problem. I use the following drill: 

The feeder faces me. Two potential receivers stand behind the feeder. When I say go, I pass to the feeder. One receiver breaks left, the other right. Only one receiver calls for the ball (they decide between them each time). The feeder pivots as son as she has the ball and MUST pass to the girl who has called for the ball. 

Once they are are doing this quickly, I add one defender. Again, the feeder doesn't know which player is open until she pivots - she must only pass to the undefended receiver. 

Once this is working I then add a second defender so that the receivers have to break and the feeder has to choose who to pass to just like in a game. I found this drill (over a few weeks) did help speed up their decision making for faster passing. 

Good luck.