I wonder if she had a painful BM in the potty place? I had an Irish Setter who had, unfortunatly, ulcerative colitis. After a painful time, she avoided the large (30x80 feet) pen we had next to the house. I had to open up the big yard for her for a week. She did fine after that.
Other than that, I'd go back to the basics and not let her out of her pen until she does poop, if you catch her needing to go. (on a funny note, I once tried to get the irish setter to 'go' poop when it was raining. It took 1/2 hour in the rain before she finally went. I knew she had to go, 'cause she had asked to go out, and then decided she didn't want to go in the rain. We were both rather wet to say the least, but I won!)