The Mother Superior presents an additional wall between Jean and Sister Irma. (The first wall is the distance between them.) The Mother Superior writes Jean to inform him that Sister Irma will no longer be taking classes. Jean never has a correspondence with Sister Irma, which is part of why Jean was so frustrated. Sister Irma, like happiness, seemed to be moving further and further away from Jean.
That Jean was able to let Sister Irma go, as determined as he was to encourage her art, is a telling indication of how much he has changed. If he made the right decision in not contacting Sister Irma, the Mother Superior can be seen as a benevolent force protecting both Jean and Irma. If he made the wrong choice and Sister Irma really did need him (though there is no indication that this is the case), the Mother Superior can be seen as a malevolent figure, a censor who stands in the way of the happiness of others. What do you think?