Complex sentence: Her writings, attributed by herself to visions and dictations word by word from the Virgin Mary, in elegant Spanish, contain both terrestrial and spiritual detail, that were either not known or not totally accepted at the time.
Split into simpler sentences: Her writings, attributed by herself to visions and dictations word by word from the Virgin Mary, in elegant Spanish, contain both terrestrial and spiritual detail. Those details were either not known or not totally accepted at the time.