"Chapter 67—Ancient and Modern Sorcery The Scripture account of Saul's visit to the woman of Endor has been a source of perplexity to many students of the Bible. There are some who take the position that Samuel was actually present at the interview with Saul, but the Bible itself furnishes sufficient ground for a contrary conclusion. If, as claimed by some, Samuel was in heaven, he must have been summoned thence, either by the power of God or by that of Satan. None can believe for a moment that Satan had power to call the holy prophet of God from heaven to honor the incantations of an abandoned woman. Nor can we conclude that God summoned him to the witch's cave; for the Lord had already refused to communicate with Saul, by dreams, by Urim, or by prophets. 1 Samuel 28:6 . These were God's own appointed mediums of communication, and He did not pass them by to deliver the message through the agent of Satan. PP 683"
"And when Saul enquired of the Lord, the Lord answered him not, neither by dreams, nor by Urim, nor by prophets."
Ellen White directly references 1 Samuel 28:6 in this passage.
"The message itself is sufficient evidence of its origin. Its object was not to lead Saul to repentance, but to urge him on to ruin; and this is not the work of God, but of Satan. Furthermore, the act of Saul in consulting a sorceress is cited in Scripture as one reason why he was rejected by God and abandoned to destruction: “Saul died for his transgression which he committed against the Lord, even against the word of the Lord, which he kept not, and also for asking counsel of one that had a familiar spirit, to inquire of it; and inquired not of the Lord: therefore He slew him, and turned the kingdom unto David the son of Jesse.” 1 Chronicles 10:13, 14 . Here it is distinctly stated that Saul inquired of the familiar spirit, not of the Lord. He did not communicate with Samuel, the prophet of God; but through the sorceress he held intercourse with Satan. Satan could not present the real Samuel, but he did present a counterfeit, that served his purpose of deception. PP 683.2"
"So Saul died for his transgression which he committed against the Lord, even against the word of the Lord, which he kept not, and also for asking counsel of one that had a familiar spirit, to enquire of it;"
The EGW passage directly quotes 1 Chronicles 10:13 to support its argument about Saul's rejection by God due to consulting a sorceress. This is a clear and direct reference.
"Then said Samuel, Wherefore then dost thou ask of me, seeing the Lord is departed from thee, and is become thine enemy?"
While EGW quotes 1 Chronicles 10:13,14 directly later in the paragraph, the connection to 1 Samuel 28:16 is thematic. EGW interprets the event in 1 Samuel 28 as evidence of Saul's rejection by God, which is also the theme of 1 Samuel 28:16 where Samuel states that God has become Saul's enemy.