In an event over the weekend, speaking on marriage equality, "That's a lie." said Obama, "And it's not always enough to lean in, because that s**t doesn't work all the time", she said at the Barclays Center in Brooklyn.
"My advice to young women is that you have to start by trying to get those demons out of your head", she said. "It's not always enough to lean in, because that s**t doesn't work all the time".
CNN's White House reporter Kate Bennett praised the former first lady for her "authenticity" in using an expletive in public.
"Marriage still ain't equal, y'all", Obama said to the packed room.
"I didn't want to just follow his Jetstream and I knew I wanted to be a woman with my own identity and own sense of self so I couldn't get lost in his journey". Sometimes that stuff doesn't work.
And despite living in the country's most famous house, Mrs. Obama has said the girls still dealt with normal teen rites of passage - including the prom.
Some Obama fans were so overcome by hearing her utter the expletive that they reacted in the extreme, saying their lives have "been forever changed".More news: Ex-Seahawks player Brandon Browner sentenced to 8 years for attempted murder
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While Obama has not criticised Trump directly at events to promote her memoir, she does criticise him in the book.
"What's inspiring to me is that so numerous young women I've met ... are triumphing in incredible ways", the 54-year-old added.
But Obama graduated from the select Ivy League university and went on to Harvard Law School before joining a Chicago law firm where she met her future husband and then USA president Barack Obama.
She added: "People will literally take our voices, they will take the things from us that they like, the size of our hips, our style, our swag, it becomes co-opted but then we are demonised".
"Malia and I were talking recently about all the little things we'd stress over in junior high and high school - whether we're wearing the right clothes, a snarky comment somebody made about us, the boys we crushed on, and on and on and on", Obama told Good Housekeeping.
Per CNN as of Friday Becoming had sold over 2 million copies in all formats and editions during its first 15 days, in the US and Canada. Many on social media praised Obama for being "real" about the struggles working women face. "Finally", tweeted one person.
She writes in the memoir that she first visited Elizabeth Garrett Anderson (EGA) school in 2009 and was not prepared for the powerful emotions she felt. "It is hard", she said according to Vanity Fair.
"I say all that to say all that while his death was sudden it was always looming for us because he was also the kind of man who wouldn't get help. I think it's okay - it's good, even - to do that", she added.