I feel like this is sort of where I am with my roommate. I was the one who introduced her to church and basically took her every time there was something going on. Now that we have lived together for the past year (away at college) we have both had some eye opening worldly experiences that have changed us. I have realized just how hard it is to truly trust and rely in God. I love Him and am working on 'waiting for Him' as we should. She however, has totally taken the wrong direction and gone down the wrong paths. Living in the world I guess. I wish it was easier to direct friends. I feel it's hard for me to share my faith even though it's all I can think about when we are around each other. I feel like I will just push her away if I share how I feel about her drifting away from God.
About your friend, I don't have sound advise about truly opening her eyes to a wonderfully forgiving and merciful God but maybe it's something that she feels isn't necessary. Like reading the bible or truly trusting it's truth. I don't know exactly how to reach out to a friend who already feels their faith is "fine" or who feels like their 'soul' is already saved. It's one thing to trust God but it's another level to have Faith in the One and Eternal Savior.
God bless you in your courage to reach out to her and I will certainly try to remember your struggle as I deal with my similar one.