I don’t like reformers, and I hope you never try to be one; reformers are apt to forget that people can be led by a little kindness oftener than driven by much scolding, and I like the sort of goodness that makes itself beautiful first, and then others wish to copy it.
Amy’s irony is that she reforms by grace. Contrast between kindness-led and scolding-driven reveals her method. Beauty leads, then teaches. In context, she pushes back on Jo’s bluntness in society. The longer pull preserves affection while stating a style. Readers see multiple paths to good. Gentle can still be firm.