This paragraph from her autobiography tells why she felt compelled to share her visions with the world:
Thou knowest, O my God, from whom nothing is hidden, that the reason why I have written these things, so much against my inclination, is that I have profited so little by Thy liberality that I cannot believe they were made known to me for myself alone, since Thine eternal wisdom cannot be deceived. Grant, then, O Giver of gifts, who hast so freely and unreservedly bestowed them on me, that whoever reads these things may be touched with tenderness and compassion for Thee. Knowing that the zeal which Thou hast for the salvation of souls has induced Thee to leave such royal gems so long in my defiled heart, they may praise, adore and extol Thy mercy, saying with their lips and with their hearts, "Praise, honour, glory and benediction be to Thee, O God the Father, from whom all things proceed," thus to supply for my deficiencies.
I love the image of a God who has such zeal for the salvation of souls that he pursues us and uses our friends and neighbors and those who love us to bring us the story of His great love. We can learn a lot if we are willing to listen.