It is very encouraging to see your concern for your friend.
Suicidal thoughts cannot be dismissed as trivial and must be addressed. Such thoughts are usually a part of depression. Now depression is a broad spectrum ranging from mild ‘feeling blue’ to serious ‘clinical depression’.
The best thing you can do for your friend is to be with her. All of us feel depressed some time or the other and most of us have had suicidal thoughts. Even in the Bible, Job and Elijah had clear signs of depression and suicidal thoughts. In Job’s case, his friends were unhelpful because for the most part, they were bent on providing answers and ‘explaining’ things while he was miserable. Your friend will benefit most from just you being there with her and starting a gentle conversation. Praying for her before you meet her and praying for her regularly will help you to discern better. If she is willing to speak further, then you may ask her further questions and try to answer them appropriately. Just having someone to talk to and discuss issues in a non-judgmental setting is very therapeutic and helpful to many.
You mentioned that you are concerned about her salvation. You should perhaps address this only after she is out of her depression, in my opinion, but this is a matter of discernment which only you can decide. Never push things. If you feel that her suicidal thoughts are pervasive, that is, they are present all the time, then she may be seriously depressed and may benefit from a consultation with a competent psychiatrist or psychologist.
We are called to bear each other’s burdens and if you can identify some issue that you can help out or someone else can help out, then that will be useful. Love her and be gentle as Christ has loved you.
Galatians 6:2 - Carry each other’s burdens, and in this way you will fulfil the law of Christ.
John 15:12 - My command is this: Love each other as I have loved you.
Pray, and as the Spirit of God leads you, you could be creative in the way you love your friend. The greatest contribution from your side will be your regular prayers for her and then, your presence. I will be praying as well.