Answer:
Form two lines with the shooters deciding which line shoots next!!!
With the shooters deciding when to shoot next, Helena wouldn't be aware of when they are going to shoot. This means she can focus on her reaction time. If she knew when they were going to shoot, it wouldn't help her.
If the shooters gave her a signal of when they were going to shoot, or if she gave them the signal, it would not benefit her reaction time. In an actual game, you don't know when the opponent is going to shoot. So, if the shooters decide when to shoot, this will help her reaction time.
Hope this helps. :)