breast cancer options with dermatomyositis

Hello - I was referred to this board from some very kind and helpful folks elsewhere here on this site.

I am trying to gather as much information as I can for my sister who has breast cancer. She was diagnosed with dermatomyositis about 2 1/2 years ago, after a very scary and life threatening flare-up that left her unable to swallow for a time, and required emergency admission to the hospital, a month stay, and then a long rehab. 

She had a mastectomy almost 2 weeks ago, and had been told that radiation is not a viable option because it could worsen the DM (which the cancer has already done),and she is not interested in chemo as she feels the effects outweigh the benefits, especially given the inter-relationship between cancer and DM, with each negatively affecting the other. 

The surgeon today told her that one of the lymph node specimens they took during the surgery is positive, which of course is not the news we were hoping for. The surgeon would not give her any further information regarding stage or type, but is referring her to an oncologist. We are now waiting for a call regarding when that appointment is available. 

Has anyone here had these two diagnoses concurrently? I would love to give her solid information from those who know first hand what this situation might hold, and whose experiences may help her make the best choices for her own course of treatment.