Dear Anonymous Girl,
- How do you know God wrote the Bible and that they were telling the truth that God wrote it and weren't making things up?
We believe, because we have faith and we can only obtain faith through Grace.
This portion of the Catechism should help:
We believe Jesus Christ is True God and True Man. Because of this, He can neither deceive nor be deceived. He chose to build His Church on St. Peter and his successors and promised that He would be with us until the end of time, not necessarily on Earth as the Man but after His Ascension through the Holy Spirit which would guide our popes and bishops.
As to why we know that they weren't making things up. The answer is simple:
Human nature and mortality tell us that people won't die for a lie and all the Early Church saints died for the faith your friend holds on to today! That's just History 101.
I don't know how to reassure her that God truly wrote it through the authors by the Holy Spirit.
You reassure her by either going online or to a local library and looking up the Council of Rome.
The Bible does not tell us What the inspired books of the Bible are nor, from a Protestant view, does it give us any inspired table of contents anywhere in the Scriptures.
The approved table of contents you have in your Bible was first chosen in 382 A.D. at the Council of Rome under the direction of Pope Damascus I. (366-383 A.D.)
So every time a Protestant opens a Bible to read it, they are re-affirming that:
The Pope and Catholic Bishops got it right!
Read the whole issue here:
If your friend is still having doubts, she should pray for the grace to have these doubts resolved.
My colleagues may have more to add.