You can see in this photo that the pup is still attached to the placenta. In the last photo, the pup is now free of the placenta. The Mom is bonding with her actual pup in these pics. You can see her talking to it and loving on it to learn it's smell.
In this picture, the Mom is protecting both babies. I would see this behavior again the next day when i came back. Luckily this Mom was in a corner of the beach and had not moved, so I could feel confident that it was the same one, plus she had the two pups still.