Recently my sister, who was saved and baptized as a little girl at the same time that I was, has confessed that she was not at all convinced that there is a God, that we believe in something that there is no proof of, and that anyone could have written the Bible. What can I do to show her the direction to look to confirm her belief in God?

Here are a couple good links to give you some ideas of what things you might think she would relate to... or at least consider:

Simple Reading:
Apologetics.com: Challenging Believers to Think and Thinkers to Believe

Heavier Reading:
Fr. Copleston vs. Bertrand Russell: The Famous 1948 BBC Radio Debate on the Existence of God

The bible has proven a lot of things that has happened to be true and you can explain this to her. Also there are books about out of body experiences and people almost going to heaven, etc and you need to buy her this book which I promice will strengthen her faith because being out of church for a while can weaken ones faith. I am not sure if she has been out of church for a while but she needs to get back in or she will fall further from her faith and will believe anyone. Get her into church and make sure that she attends every week. Buy her an easy to read and understand Bible and buy her some encouragement and faith books. Buy her some books also about the out of body experiences, so that she can see from other peoples experiences and this will bring back some of her lost faith. Pray for her also and this is about all that you can do!

I don't think it is your position or right to push God on her. If she feels that perhaps she doesn't not believe then that is her choice. Not yours. It doesn't make her any worse a person. Many people are not convinced that there is a God. There are arguments for both cases.

Just let her make her own decision and love her like a brother should. Unconditionally.

The best advice I can give you is to pray for he's so that God can open up her spiritual eyes. We don't serve God by what we humans know but by faith. The bible says that many are called but few are chosen. Many times we are trying to solve things on our own but at the end it is God that knows best.

The best thing you can do is pray for her. It takes faith to believe in God and the Bible says without faith it is impossible to please him. (God) I will say this, IF she was really saved as a child, she is still his. Many people go through times of unbelief and the Lord draws them back to himself. But if she was just going through the motions, she may not be saved. Either way, prayer is the BEST thing you can do.

We each have to fight our own demons of disbeleif. And proof to you, may not be to her, since to be honest you can't PROVE he exists, it is a matter of faith, of trust and of feeling him in her heart.

Has something happened to create doubt, some event in her life ?

To be I merely have to look at nature, all the different types of trees, the rivers, the fish, the birds in the air, all of the nature God has created.

And at MAN in his arrogance and nature. How could all of this come to be, some spark in some pool or goo ( and then where do that come from to start with) and a maple tree could ot become a squirrel, that is just real sillyiness but someone would want to believe that over a loving god, or even a hateful god. But for me, to see the cows in the field, or to stand at the edge of the ocean and realise how small I really am in all of this. That is where I find God, in his works. But he can be found in his writings, that men died for over thousands of years to provide us with that history.