Perfect song about forbidden love?

My best friend and I love each other, but she's married. We've talked about our feelings but we both agree that we can't ever be together. She's older than me and she has a husband and children. It wouldn't be right. I want to burn her a song on a CD and leave it in her car. Sort of "I love you, I'm here for you, and I don't regret the way I feel about you". I wish things could be different, but they can't. I need the PERFECT song. Nothing too slow or cheesy and no Taylor Swift or Whitney Houston. I was thinking something along the lines of something like Dave Barnes, Matt Wertz, etc. but I am open to anything.