The others have given wonderful advice, as always. There are few things that I would like to add . . .
The most shocking and best thing that I heard from a friend was "You are so lucky!" You have been diagnosed now - my mom and 3 of my sisters have had breast cancer and the technology is so much better for you than it was for them. Whatever you want, need or whatever, I am there for you, just let me know. Then, she brought me a gift (the first of many) jammies, and a big fuzzy warm bathrobe. She followed that with the gift of truth. Whenever I got depressed, upset or whatever, she (figuratively) smacked me in the head and brought me down to earth - - - she let me know that my feelings right then were valid and told me how "WE" would get through this together along with all of my other friends and family.
Now the most amazing part of all of this is that she was merely an acquantence - I found out that people who barely know you can and will turn into angels in a heartbeat. She is now someone that I consider one of my best friends. Some of my best friends can't handle what I'm going through so they don't call or talk to me.
Three years later I have another "scare" happening and I have talked to her about it and will tell her the results before I will tell Mom.
I hope that you can be this friend for Amy. This is the best thing that could happen to her and for her. Be positive, but never, ever let her forget reality.
L & H,