Mild case of copd life expectancy?

My mom was said to have copd and was diiagnosed through an x-ray and no other tests.It was said that her case is mild and she quit smoking right away.My question is will this kill her or since she only has a mild case and if from chronic bronchitis will she have a normal life expectancy? My mom is only 46 so hearing this made me so sick to my stomach and auomaticly i jumped to conclusions.I am only 23 and i have a daughter who is 2 tomorrow and i am also 17 weeks pregnant.I want my mom to be around to see my children grow up and since i am still young i don't know what i would do with out my mother if she was not around.She is not just my mom but my best friend and it just breaks my heart.If you can answer my question pls leave the site with the info and if your a doctor even better :)