This may or may not have been a "dark night". Some of her other comments incline me to think she had no supernatural faith - but God alone knows.
I would suspect she was a Roman Protestant front, who did some good work in a country, India, where the poorest of the poor were said in fatalistic fashion to almost 'deserve' their fate. And she said, no, they didn't. And she tried to comfort some in their last hours. For others, she was accused of letting them suffer, because suffering is good . . well. She was accused of financial mismanagement, of not knowing where the money was or went, and of hypocrisy in preferring first class medical treatment while stripping the various convents of superficial trappings, like carpeting. And so on. It did seem that some of what she was about was - for show.
That's never good.
She also spoke against permissive abortion. This is something the Roman Protestant bishops increasingly stopped speaking against, at least so publicly. She seemed, spiritual, in a way, but not necessarily in a Catholic way.
That was the complaint of Coomaraswamy, of course, when he wrote to her about her comments suggesting indifferentism. She replied with what seemed vague confusion and then passed off future correspondence to some 'expert'. But Coomaraswamy, along with 'getting' the idea that 'new church' really was a new church, and very different from Catholicism, also seemed to 'get' what was going on with Mother Teresa of Calcutta. Had it not been for Muggeridge's promotion, who knows if some of the criticisms of her might not have been taken more seriously, rather than relegated to a Commie debunker, with little credibility, like Hitchens.