First, you will have to pray for her mind and heart to be opened to the Spirit of God.
Without this, she wont listen to the godly advise of anyone, including God.
I remember people giving me advise (godly advise). The dumb thing is, I was searching for it, but was unwilling to listen to it. Because it wasnt what I wanted.
We have to open to the truth, even if it isnt what we want. And then be willing to obey.
So, I would pray for this for your friend. Pray that God will open her eyes and ears for Proverbs says, "Ears to hear and eyes to see are both gifts from the Lord."
And Isaiah says, "You will hear my words, but you will not understand. You will see what I do, but you will not percieve its meaning. Harden the hearts of these people. Close their ears, and shut their eyes. That way, they will not see with their eyes, hear with their ears, understand with their hearts, and turn to me for healing."
Pray that God will open up these things in her, so she can recieve a healing.
And when you pray, dont let any secret motives enter in. Stay pure in your prayer for her. Let it be totally about God and her. About God's desire for her life.
And also remember this, we are told to pray for those who despitefully use us. So pray for this person, whom despite everything she loves. And remember, despite everything God knows about us, he too loves us.
God be with you.