Pupcake

I have noticed that Cassandra constantly seems hungry, even after she just eats. She will scarf her food down and then lick the bowl for about a minute or so then start sniffing around searching for more food. She tries to eat anything she picks up on the floor even if it's not eatable. Is this normal? She is fed twice a day (once in the morning and once in the late evening) and she is given probably 3 treats inbetween then. I feel bad because she is always hungry and want to give her more food to see if maybe that would make her happier but with the Evo my vet said to only give her what was directed because she is gaining weight now and she doesn't want her to get too fat (plus Cass gets sick if we give her too much more Evo a day). Is it normal for a dog to act like it is constantly hungry? She's been checked out by two different vets and they both say she is in perfect health and she has had full blood work done for both vet places.