To answer your question see my post in the general lung discussion "entitled tarveva may have another success story."
My mom has adenocarcinoma, with a Stage IV met to brain. Based on my research on Tarceva, if your mom was not a smoker the chance of success is much higher. The Drug was approved in the US in Nov, 2004. And I believe also was approved in Europe. Another experimental drug actually the first to come out on this subject, is called Gefitnib also known as Irresa, which I personally believe is probably just as good, its just they got unlikely with a second clinical because they didn't test the right kind of people.
With both Tarceva and Gefitnib I think its an all or nothing type of thing. If it works it can work from 10months to 3 years.
Based on what you described, if your mom never smoked, I would recommend you try like hell to get your mom this drug because results could be very positive. From what you described your mom fits two of the key factors, mainly adenocarcinoma and she is a women. If she is a never smoker, I would say chances are Tarceva will work.
Also check out the internet the spelling of the drug is "TARCEVA" not "terceva" you will find many hits on this drug. It working miracles on my mom, how long is a big question, BUT for now it has provided not only relief from the cancer, but hope for everyone.
Good luck!!