The Problem with Sr. Chittister is that she left Roman Catholicism a long long long time ago.
She still has a very significant following among the "peace and love" crowd. I think it's a shame because it's very difficult to take Catholic teachings on many social issues seriously when they are espoused (and often "explained") primarily by people who do not believe in the teaching authority of the Church at all. Sr. Joan is near the top of the list.
God gave us each free will. Because of free will, we are able to formulate our own thoughts and ideas and believe whatever we want to believe. The obvious danger is that each person can then decide what is right and what is wrong. What may be right for one person, may be wrong for another. What is wrong for one person, may be right for another. It is chaos! We are each left up to our own imaginations and there is NO absolute right or wrong.
That is one reason God gave us His Word. So that we each don't have to try and figure out what is right and what is wrong. God's Word represents ABSOLUTE TRUTH, and is the final authority in all matters of life. Of course, people still have the free will to decide for themselves what they want to believe, but just because someone decides to reject God's Word, makes it no less true.