The writer for Yahoo! Shine shouldn’t feel bad about herself for making this mistake — a lot of people (especially if they write for Yahoo!) make the same grammatical goof:
As I’ve said before: If you’re trying to pick out a ripe peach by gently squeezing the fruit, but you’re wearing oven mitts, you might feel badly. If your emotional state is sad, depressed, anxious, or unhappy, you might feel bad.