Why not surgery?

Hello all.  My mother was diagnosed with lung cancer (Adenocarcinoma) and brain cancer on New Years Eve.  Both tumors were very small about three centimeters.  The only  reason we figured it out was because the small brain tumor was sitting right on the area that affects her speech.  She underwent radiation for the brain and I am told it "is still there, but is effectively dead."  I don't understand this. After the radiation was complete.  She started on chemo.  Six hours every three weeks.  I barely talked to her during this time.  It completely wiped her out.  The tumor shrunk from about 3 centimeters down to about one.  But, her latest scans showed it growing again.  So, she is back on chemo.  Only 20 minutes, but it is kicking her butt again. This is hard for me because I am in a different state and they are in a small town.  I feel like I only get half answers on the treatment.  What I don't understand, is if the tumor is so small, why not do surgery to remove it.  Is that not a normal course of action?  It seems like she is going to continue to do chemo and her life just sucks while she is on it. Any insight you could give would be great.  I understand you don't know her medical history, but any input would be great.  My mom didn't even want me to send off her records to get a second opinion on treatment because she loves and trusts her doctor and nurses.  I just feel really helpless.  Thanks!