I'd give the treats seperately; so she doesn't try to guard / snatch / gulp hers to get to Mia's treat too. I had this issue with my 3, so I seperated them with a baby gate and they had treats seperately. Now they sit to have a treat, and don't snatch. Initially I gave the treat in a closed fist, only opening my hand when the dog was sitting.
Now, if treats are offered; the three dogs accept them, then run to their respected 'safe spot' to eat them
(Meg under the stairs, Ruby to hall, Gemma to the dining room; it's quite funny to watch now; but I stay with Ruby, as she is a slow eater, and Meg will try to steal
I don't want Ruby to start to resource guard her treats and toys.
ETA - do you have any problems at meal times? Do they eat near each other ? Or do you have to seperate them?