Hi Cass,
Your sister's story sounds very similar to mine. My lump was in the milk ducts as well. The best advice I can give you is this:
make sure that she is put in touch with a breast care nurse, this will be a valuable relationship to have.
Go along to her appointments with her, as it will valuable to have someone else there when hearing about treatment options.
Also it helps if you have a surgeon who you can get along very well with and doesnt mind explaining things to you mutlipy times.
And the Cancer Council in your state is very handy to visit, and also we are all here to answers questions for you.
Wishing you all very best, and don't forgwt to take care of yourself as well!
Donna xo