I think that if it is working well for you, then it is a great idea. I know that when I livd out in the country, if there was some kind of a fight with the cats, or even with the dogs, the aggressor was promptly thrown out the back door and left out there to think about his rowdy behavior. Usually, it gave them the idea that they were not the king/queen of the house, and could not get away with just bossing the other cats or dogs around.
By feeding the younger one first, if you always do that, then she probably assumed that she was the number one cat, and had the right to all the food, so she decided to show the older cat that he could not eat unless she allowed it.
When you put her in time-out, she had to realize that she could not behave that way.
