Ida is a person who just follows wherever she's led, does whatever she's told. She made a decision to see her parents' burial place, but that wasn't much in the whole scheme of things. In the very last scene, she is walking back to the monastery-- a personal decision that is completely hers. She now knows who she wants to be and has enough information to make an informed decision.
It is a powerful act of independence, although most people might see it as the opposite.