"Chapter 34—Can Our Dead Speak to Us? The ministration of holy angels, as presented in the Scriptures, is a truth most comforting and precious to every follower of Christ. But the Bible teaching upon this point has been obscured and perverted by the errors of popular theology. The doctrine of natural immortality, first borrowed from the pagan philosophy, and in the darkness of the great apostasy incorporated into the Christian faith, has supplanted the truth, so plainly taught in Scripture, that “the dead know not anything.” Multitudes have come to believe that it is spirits of the dead who are the “ministering spirits, sent forth to minister for them who shall be heirs of salvation.” And this notwithstanding the testimony of Scripture to the existence of heavenly angels, and their connection with the history of man, before the death of a human being. GC 551"
"For the living know that they shall die: but the dead know not any thing, neither have they any more a reward; for the memory of them is forgotten."
EGW directly quotes Ecclesiastes 9:5 to support her argument against the idea that the dead can communicate with the living.
The doctrine of man's consciousness in death, especially the belief that spirits of the dead return to minister to the living, has prepared the way for modern spiritualism. If the dead are admitted to the presence of God and holy angels, and privileged with knowledge far exceeding what they before possessed, why should they not return to the earth to enlighten and instruct the living? If, as taught by popular theologians, spirits of the dead are hovering about their friends on earth, why should they not be permitted to communicate with them, to warn them against evil, or to comfort them in sorrow? How can those who believe in man's consciousness in death reject what comes to them as divine light communicated by glorified spirits? Here is a channel regarded as sacred, through which Satan works for the accomplishment of his purposes. The fallen angels who do his bidding appear as messengers from the spirit world. While professing to bring the living into communication with the dead, the …
"And no marvel; for Satan himself is transformed into an angel of light."
Both passages discuss Satan's deceptive nature and his ability to appear as something good or holy to deceive people. EGW's passage specifically connects this deception to spiritualism, while the Bible verse speaks more generally about Satan's disguise.