At the risk of being called a total idiot, I'm going to share my opinion on this particular issue.
Remember when Cindy said Casey couldn't sleep in her own room while at home? That she slept on the floor in their room? I also think (likely everyone will disagree with me here also) that SOME of the tears Casey shed behind bars as seen in jail videos are genuine when thinking about Caylee.
While this woman is sure as hell not up for Sainthood, I do think something happened to Caylee that wasn't supposed to (her actions after the fact not included) and that she does have some level of heartache/remorse. It's burried deep...but it's there.
I think the jail called the Pastor, or maybe he decided on his own to come up there? My guess is that Casey felt that she might say more than she should, given the news of the day, and didn't want to "risk" it. She might also have felt (and this would be against her character for sure) that at that time, LYING to a man of faith wouldn't be the right thing to do.
Her turning away her Pastor, to me anyways, says that she is feeling some level of guilt or remorse.
JMHO.