Am I close to getting the Maggie minigame?

I find it quite simple: turn the volume up to maximum, then start the game. As soon as the countdown is finished, browse through your Springfield systematically, meaning in a way so that you cover the entire area in a short time. You don't need to be slow. You will hear only the sound of the Monorail and Maggie's typical pacifier sucking sound. As soon as you hear the latter, stop your search and move only in small steps. You will hear Maggie's sound again when you come closer, and softer when you move away. Then it may be good to zoom in, you'll find her, unless you have covered your buildings with some things that obstruct the view on the building.
Usually, I have found her by just searching the Maggie-Sound before the time allowed has reached 30 seconds, and within those 30 seconds it is easy to find her in the comparatively small area.