My experience with this problem is this:
Make eating the shit as unappealing as possible. Leave a couple landmines out in the yard but cover them in habenero or tabasco sauce. Whenever your dog DOES eat some crap make sure she is scolded, if it is a very bad case you may even need to resort to dominant actions like pinching the neck or tapping her hind quarters.
But of course dogs respond better to positive reinforcement than negative, so when she does come back from a successful outing of no poop eating give her a treat and praise, and continue to scold for eating scenarios.
Dogs are a byproduct of consistency. 1-2 months of diligently reinforcing both actions in the appropriate way will typically end in success.
Hope this helps!