Here are possible solutions to your problem:
1. Change your dog's diet. Buy quality food that is formulated for your dog's age and breed.
2. Feed your dog a little more if she is still asking for it.
3. Take her to your vet so they can run some examinations on her.
4. Clean her up right after you caught her eating her feces.
What you are dealing with is called Coprophagia. It is not all that uncommon a behavior, especially in puppies. Some grow out if it and some don't.
There are some things you can try adding to the food that may help. One is called Prozyme and another is For-Bid.
Another method some have tried is adding pineapple, Brussels sprouts or cabbage to the food. Before you try those, consult your Vet.
You can try letting the puppy only use one area for dedication and keep it picked up as soon as she goes.
I have heard of people keeping hot sauce handy and putting it on the poop, theory being the pup will not appreciate that and stop the habit.
Don't let her out without you with her. Take some treats or a favorite you. If she poops, distract her away from it right away with the toy to distract her.
Blonde is right that it may be she is finding her excitement tasty so you might try changing foods.
Hopefully, she will grow out of it.
Do an Internet search on Coprophagia and read up on it.
Good luck!
I had the same problem with my dog and this is what I found out from my vet. Because I am feeding her high quality dog food seems it tastes great the second time around so thats why they eat it. Its gross I know. The only way to make her stop was to add a cheap can food to her food. Just like a couple of teaspoons and mix it in with it. Seems it make the stool not as appetizing. You might want to give it a try.