Yes, mets to the brain would indicate stage IV.
Non-Small cell adneocarcinoma (sp) is often in non-smokers and women.
That is what my husband has. Although he did smoke some in his earlier years he was never a "smoker". He was around 2nd had smoke a lot in his work environment. And, RADON gas is know to be a large contributer to this cancer.
There are a number of very good web sites with more info.
I wish your friend and you the very best.... it will be a trying time for all of you.