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Friwi, horse crap would be one of the favourite for a heap of dogs as it is only partially digested. I would imagine rabbit would be the same.
We have some dogs at work that eat their kennel mates...

Like with all training you need to let her know that it is not ok to eat crap. I'm not sure if you actively discouraged her from eating the other dogs crap, if not then she would have regarded that...