To be fair, here is the First Lady's full response:
"Absolutely not," Mrs. Obama answered when a girl at a "take our daughters and sons to work day" event asked if she would ever run for president. "I think one of the things you learn about yourself as you get older are what are your strengths and what are your interests. And for me it’s other stuff that is not being the President. So I probably won’t run."
So, that's an "absolutely not" followed by a "probably won't." But we're going to go with the "probably won't" because that's much more interesting! Maybe she'll run in 2016 against Hillary Clinton and Andrew Cuomo and Jeb Bush and Chelsea Clinton and Liz Cheney and Mario Cuomo!