The line everyone knows, that all shall be well and all shall be well and all manner of thing shall be well, is not a reassurance about circumstances. It is the answer she is given to a specific and unbearable question. She asks why sin was permitted at all, since without it everything would have been fine, and the answer she reports is that sin is necessary, behovely, and that this is nevertheless true.
She does not pretend the answer resolves the difficulty, and the honesty is what makes the book hold up. She states plainly that she saw no anger in God, none at all, and then sets that against the teaching of the church, which she also holds, that sinners are condemned. She does not harmonise them. She reports both, says she was shown a parable of a lord and a servant which she could not interpret for nearly twenty years, and eventually reads it as showing that what looks like the servant's fault is seen from above as the servant's injury.
The other thing she is known for is worked out at length rather than dropped as a figure of speech. Christ is our Mother: he bears us, feeds us with himself as a mother feeds with her own body, and does not leave a child that is hurt. She develops the theme across chapters, with the ordinary Trinitarian language beside it. Her book was almost unknown for five centuries and survived in a handful of manuscripts; it is now the most widely read work of English mysticism.