Now this chapter was primarily about the voodoo lady being evil, as many have speculated, but even still I trust her due to her words and especially after LeChuck murdered our hero. My thoughts on all of this is that the voodoo lady has used her powers to look into the future and see all these events unfold. She records them all in her journal and realizes her role is to simply act as a guide to others. She cannot tell Guybrush the future as that would be tampering with destiny, the bigger picture she mentioned in jail. That also fits with her saying she has never lied to Guybrush, but withheld information so that others are still given a choice and a free will.
She sees that LeChuck would have always been an evil villain one way or another and so his destiny was always to be a villain. How LeChuck got this journal is another matter entirely, but he saw it as the perfect opportunity to frame the voodoo lady and finally stop her from meddling in his plans. Therefore, the voodoo lady knows everything, but never planned it, just saw it in the future. She told no one of it as that would be tampering with the fabric of life. She allowed people to make their own choices and determine their own destinies. She has never lied and has always cared for Guybrush and Elaine. LeChuck was always meant to be a selfish and demonic abomination.
Well, that's my take, any other thoughts my friends?