Here, Isabelle lies to get what she wants. In another show of kindness, Beck promises to get her a train pass. Beck probably thinks that, if nothing else, it is safer for everyone involved to have Isabelle out of the house. Meanwhile, Isabelle is simultaneously glad and upset that Vianne believes her lie. The lie is a test that Vianne simultaneously passes and fails, but as it turns out, Vianne thinks of Isabelle exactly the way Isabelle predicted.