Mystique only knows what Destiny said to her, that there would be a time when all the mutants would unite but would reject Destiny so she told her that if they didnt decide to bring her back then Mystique should burn it all down.
Destiny is a character used to hide information and only give enough to different people at the time depending of how she wants things to happen, for example she didn´t told Mystique she was going to be killed, this actually made Raven mad at her for years, neither did she tried to change Rogue´s mind when she joined the X-men and she told Mystique how she could save Rogue from the virus she had during Carey´s run.
So imo in the present story, she told part of the truth to Moira, she told something else to Mystique, it´s possible she left something else in her diaries and Blindfold may have known something about this situation too but Destiny is the one who knows almost everything imo, she´s key player and maybe that´s why not even Erik and Charles want her to stay dead despite Moira´s protests.