Note that Ellen White demonstrated a distinction between the words “PERSON” and “BEING.” While she speaks of three persons or personalities and powers in the Godhead, she consistently identifies “ONLY” two beings -- the Father and His Son. Thus the words “PERSON” and “BEING” have different meanings to Ellen White.
She called Jesus Christ by HIS Spirit a “PERSON,” but she obviously did not mean a literal person which has confused some. “When trials overshadow the soul, remember the words of CHRIST, remember that HE is an unseen presence in the PERSON of the Holy Spirit,” — (E.G. White, DG 185.2, 1897)
Thus when Ellen White calls the Holy Spirit a “PERSON,” she is NOT referring to another “BEING.” She is referring to Christ by HIS Holy Spirit. We also know this because she only ever identifies two beings -- the Father and His Son. And if Ellen White meant a literal person, then that would contradict all the quotes below making her a false prophet.
The Trinity doctrine claims three CO-EQUAL beings, but notice that the quotes below from Ellen White state there are “ONLY” two beings and that there is the Father and Son “ALONE” and hence there cannot be a third being.
Note that Ellen White wrote “ALONE” and “ONLY.”
“The Father and the Son ALONE are to be exalted.” — (E.G. White, YI, July 7, 1898) -- TWO BEINGS ALONE
“God and Christ ALONE know what the souls of men have cost.” — (E.G. White, ST, Jan 13, 1909) -- TWO BEINGS ALONE
“God informed Satan that to his Son ALONE he would reveal his secret purposes, and he required all the family in heaven, even Satan, to yield him implicit, unquestioned obedience;” — (E.G. White, ST, Jan 9, 1879) -- TWO BEINGS ALONE
“Can anyone consider the condescension of God in preparing the gospel feast, and its great cost, and treat the invitation slightingly? No man, nor even the highest angel, can estimate the great cost; it is known ONLY to the Father and the Son.” — (E.G. White, BEcho, Oct 28, 1895) -- ONLY TWO BEINGS
“The ONLY Being who was one with God lived the law in humanity, descended to the lowly life of a common laborer, and toiled at the carpenter's bench with His earthly parent.” — (E.G. White, ST, Oct 14, 1897) -- ONLY TWO BEINGS
“And truly our fellowship is with the Father, and with his Son Jesus Christ.” — (E.G. White, RH, July 13, 1905) -- TWO BEINGS
“CHRIST the Word, the only-begotten of God, was one with the eternal Father,-one in nature, in character, and in purpose,-the ONLY being in all the universe that could enter into all the counsels and purposes of God. By Christ, the Father wrought in the creation of all heavenly beings.” — (E.G. White, GC, p. 493) -- ONLY TWO BEINGS
This is the truth God gave His remnant. “The HOLY SPIRIT is the SPIRIT OF GOD; it is also the SPIRIT OF CHRIST. It is that divine, mysterious emanation through which they carry forward their great and infinite work.” — (Uriah Smith, GC Bulletin, March 18, 1891, pp. 146, 147)
So while there are three entities, there are only TWO LITERAL BEINGS. The Holy Spirit is the mind, power and personal presence of God coming to us through His Son and why Ellen White calls the Holy Spirit the Spirit of Christ. It is not and cannot be a third being.