Why tell her? Leave her in ignorance or to figure it our for herself. If she is gonna be all hateful, let her stay in the dark.
When she starts giving you a hard time, hit her up with some if this:
The SDA is a cult by my estimation. If you have any other questions I will be glad to help. Below is a brief list of some of EGW Bible contradictions and false prophecies.
EGW says: The plan of salvation was made before the Fall (Great Controversy [GC], p.347).
The BIBLE says: The plan of salvation was made “before the world began” (II Timothy 1:9).
EGW says: Adam was deceived (GC, p.352, 1885 ed.).
The BIBLE says: :It was not Adam who was deceived” (I Timothy 2:14).
EGW says: The Tower of Babel was built before the Flood (Spiritual Gifts [SG], vol. 3, p.301).
The BIBLE says: The Tower of Babel was built after the Flood (see Genesis 11:1-9).
EGW says: Some species of animals were not allowed into the ark (SG, vol. 3, p.15).
The BIBLE says: “Of all the living creatures you shall bring two into the ark” (Genesis 6:19).
EGW says: Not everything outside the ark died (SG, vol. 1, p.77).
The BIBLE says: “…everything on earth shall die” (Genesis 6:17).
EGW says: Noah ate only the flesh of clean animals (Patriarchs and Prophets [P&P], p.107).
The BIBLE says: “Every creature that is alive shall be yours to eat” (Genesis 9:3).
EGW says: Pharaoh's magicians did not turn their rods into snakes (SG, vol. 3, p.205-6).
The BIBLE says: The magicians did turn their rods into snakes (see Exodus 7:8-12).
EGW says: Slaves cannot be saved (SG, vol. 1, p.193; Early Writings [EW], p.276).
The BIBLE says: Slaves may be saved (see I Corinthians 12:13; Galatians 3:2
EGW says: The Ten Commandments were written on only one side of the tablets (EW, p.32).
The BIBLE says: The Ten Commandments “were written on both sides, front and back” (Exodus 32:15).
EGW says: Jesus did not choose Judas (Desire of Ages [DA], p.293).
The BIBLE says: “Jesus replied, ‘Did I not choose the Twelve of you myself?'” (John 6:70).
EGW says: The Atonement was not finished at Calvary (Testimonies for the Church [TC], vol. 1, p.58; GC, p.422, 623).
The BIBLE says: The Atonement was finished at Calvary (see John 19:30; Hebrews 10:12).
EGW says: The blood of Christ doesn't cancel our sins (P&P, p. 357).
The BIBLE says: “The blood of His Son cleanses us of all sin” (I John 1:7; see also Romans 5:9; Ephesians 1:7; Hebrews 13:12).
EGW says: Jesus' bones were broken during the Crucifixion (SG, vol. 1, p5
The BIBLE says: Jesus' bones were not broken (see John 19:33, 36).
EGW says: We are reconciled to God through obedience to the Law (TC, vol. 4, p.294).
The BIBLE says: “…we were reconciled to Him by the death of His Son” (Romans 5:10; see also II Corinthians 5:18; Galatians 2:16; Ephesians 2:8-9).
EGW says: The seal of God is the keeping of the 7th day Sabbath (TC, vol. 8, p.117; GC, p.640).
The BIBLE says: The seal of God is the Holy Spirit (see II Corinthians 1:21-22; Ephesians 1:13; 4:30).
EGW said concerning her writings, “There is one straight chain of truth without one heretical sentence in that which I have written” (Selected Messages [SM], vol. 3, p.52). Nothing could be further from the truth as we have seen from a mere sampling of her contradictions with the Bible (for further information see www.ellenwhite.org). One thing that EGW said that I complete agree with is “If (my) testimonies speak not according to the Word of God, reject them” (TC, vol. 5, p.601). Amen, Ellen, amen!
PROPHECY: “Old Jerusalem would never be built up” (EW, p.75).
REALITY: Since 1948, Old Jerusalem has been greatly built up by the Israelis.
PROPHECY: EGW will be alive at Jesus' Second Coming (EW, pp.15-16).
REALITY: EGW died on July 16, 1915.
PROPHECY: Some alive in 1856 will see Christ's Second Coming (TC, vol. 1, pp.131-132).
REALITY: All from 1856 have died.
PROPHECY: The Civil War is a sign that Jesus is about to return (TC, vol. 1, p260).
REALITY: Jesus did not return.
PROPHECY: England will attack the U.S. during the Civil War (TC, vol. 1, p.259).
REALITY: England did not attack.
PROPHECY: The earth will be depopulated soon after 1864 (TC, vol. 8, p.94).
REALITY: The earth's population has increased greatly.
The Bible warns against “Prophets” like EGW. “Beloved, do not trust every spirit, but put the spirits to the test to see if they belong to God, because many false prophets have appeared in the world” (I John 4:1).
For further evidence see Deuteronomy 18:20-22: Ezekiel 13:6-9, 17-23; Jeremiah 23:32; Matthew 24:24; II Peter 2:1-3.