Why on God’s green earth did the Yahoo Lifestyle writer think this is correct?
I think she was going for hairdo, and became a tad confused. The contraction ‘do is often used on Yahoo in place of hairdo. The apostrophe is supposed to indicate that there are letters missing, so the writer was really describing a hair hairdo. But according to the American Heritage dictionary, do (sans apostrophe) is correct and hairdo is one word.