Question: Which much more famous artist co-writes and sings backing vocals on Kellie Pickler's 2008 song "Best Days of Your Life"?
Sentence (from "Best Days of Your Life"): The song is about a narrator explaining how her former boyfriend cheated on her and moved on to a new girlfriend to start a family with, wishing them well on their new life but says that the new girl won't top what they previously once had before.
Relevant evidence: No