Best Friend? More Like A Sister

Rosie, while it's not entirely impossible, it's highly unusual for someone your friend's age to be diagnosed with breast cancer.  So I guess my first question is, what has happened for her to believe she has breast cancer?  

Other than that big question, assuming what she's told you is true, all you can do is what you would do for any friend going through a crisis -- be there for her, ready to listen to her fears and concerns -- and let her know that you're available for any help or companionship she needs or wants.

Again assuming this is a correct diagnosis (which maybe you can tell I'm having a hard time getting my head around), you need to know that there are many types of breast cancer, and it's often not a life threatening diagnosis unless treatment is ignored.  So let's just hope that your friend will be one of the thousands of women whose breast cancer is found very early, that she gets appropriate treatment after which she will be fine and go on to live a long and happy life.

I'm really sorry this is happening to you and to her, but hopefully you can both find support here on BCO.    Deanna