
I would never have allowed the older dog go anywhere near the others food. Your younger bitch should know that you will ensure that she does not need to worry about having her food taken, and the older should know that you won't allow her to bully the younger at meal times.
I feed all my dogs in the kitchen, including visitors (some of which have tried to steal the others food) but I make sure they never can, so my girls are very relaxed over their food, and know not to go to anothers dish, so much so that I do not need to even supervise closely anymore (but I do).
As the older one looks like she is going to be in charge I would put her dish down first, and then the younger bitches. Once the older one has finished remove her from the room so the other can finish (or more likely start) her food in peace.
I am the one in charge of food, being the big alpha bitch here