What are the survival rates for someone having a double masectomy?

Our close family friend found out she has breast cancer a few weeks ago and is getting a double masectomy tomorrow (June 6). I know she probably be fine but there are always risks. Are the chances of survival good for someone having a double masectomy?
Thanks to everyone who replied back. To answer the one question, I’m not sure if she is getting reconstructive surgery. I just wanted know what the risks were during the operation and even after. We haven’t heard from them yet today, but I’m hoping everything goes well! Thanks again everyone…you’re answers really helped! Please check my other question about Limb Girdle and maybe you can answer it!

Stage and size of tumor play a big part in this. Also there are 3 main types of BC. That is important also. Another factor to consider is if the tumor is estrogen and HER 2/3 pos or neg.
One very important factor that is often overlooked is the attitude. It is very helpful to have a good attitude and a good support group. Mastectomies, and other treatments together do increase the survival rate. Today the survival rate is rising. I am a 7 yr. survivor, and wish her much luck.