So does your dog vomit her other meals during the day? Puppies need the meals to be broken up into 2/3 meals a day depending on what age they are, so I assume you are not feeding her daily quota all at once?
Depending on the breed your puppy is, that actually sounds like a fair bit of food for one meal-time TBH.
So, my first guess is that she is vomiting the meal back up in it's entirety because it was simply too much food for her stomach to handle in one go.
That to me would be the first and most common cause of this happening.
The next thing on my list would be ensuring you do not feed puppy within an hour before or after exercising etc. That can do it also, along with other more dangerous things.
The next thing on the list isn't so great, so perhaps you could answer those points I've discussed first? Cheers.