How do you say goodbye?

Hello,

My friend is nearing the end of her battle with cancer. She moved away some time ago, so I haven't seen her in years but we have stayed connected through social media. I've just heard that she doesn't have much time left. My heart is breaking and I want to call her, but how do you do that, what do you say? She was always this strong, badass lady, I think if I hear her voice and it is weak I will lose it. I know it is not "about me" right now but as a cancer survivor it is just harder, I think.  Any words of comfort and advice are most welcome.

Laura