Power player leaving White House, but not before making a promise to Obama

She has one of the most high-power, low-profile roles in the White House. If you want to see President Obama, you have to go through her.

Alyssa Mastromonaco is the White House deputy chief of staff for operations and has been serving Mr. Obama since 2005 when he was a senator. After nine years of juggling elections, wars, national tragedies and the president's schedule, the 38-year-old will leave her job next month for some downtime.

Before Obama agreed to let her go, however, Mastromonaco had to promise the president one thing: that she would be there for him after his presidency.

"We've been through a great adventure, and what he said was, 'You can go and you can take some time off. But -- you know, we're together forever, and I need you around.' And he's like, 'You have to tell me that's the deal,' and I said, 'Of course,'" Mastromonaco said to "CBS This Morning" co-host Charlie Rose in her first interview in eight years.

The president initially tried to talk her out of leaving.

"I think that he knew that for me to actually get to the point where I said, 'You know what, it's time,' that he understood," she said.

In 2005, she had just wrapped up work on John Kerry's failed presidential bid when she joined a political start-up that would eventually become a "Who's Who" of Washington. From senate office to presidential campaign to the White House, she is one of the last remaining members of Mr. Obama's original team. She is also one of the president's most trusted aides.

"I think over the years of decision-making and navigating some tough times, you know, your mettle's really tested," she said. "And I think that I proved to him that his success was my number one priority. That my hard work on his behalf wasn't self-interested. And that I had good judgment."

Mastromonaco said she and the president are "linked."

"My judgment is good judgment for him. ... I think we understand each other, and I understand what he's trying to do and how to get there."

In the White House, she is the go-to person who has the answer for everything, she said.

"I'm all over. I think the reason people think I'm so powerful is because they don't know what I do," Mastromonaco said. "And that mystery, which I have kept for good reason over the years, really intrigues people."

Mastromonaco's unassuming power has a bold impact. Her most important role is managing President Obama's time. However, her job is much broader. She runs the White House campus, which includes 17,000 employees, and she's behind the search for the president's cabinet selections.

Despite the load, the president has said to her that as soon as people see her, all her power will go.

"This is true," Mastromonaco said. "I'm a very internal person. I don't do a lot of public speaking ... but when I'm on the phone, I think I sound like the booming voice of Oz. When people see me in person, I think someone once said I look like Sally Field in 'The Flying Nun,' and that I should stay behind the curtain if I wanted people to be scared of me."

Even the president likes to kid around about Mastromonaco's height -- a running joke that reveals their close relationship.

"He fancies himself a bit of a big brother, I think," Mastromonaco said. "He likes to call me short. Just like a big brother."

She laughed and said that she is "diminutive."

"When we would travel sometimes and be on the road and it's maybe, you know, maybe not everything's going great, we can always make him laugh when we say, 'Let's talk about how short Alyssa is. Let's make some short jokes.' And then he always has to crack a smile."

Her work also pervades her personal life. In November, Supreme Court Justice Elena Kagan married Mastromonaco and David Krone, chief of staff to Senate Majority Leader Harry Reid.

"I'm not gonna lie, when we come home at the end of the day, there is a lot of work talk sometimes ... it's more about who did what to who," she said.

Mastromonaco said she's okay with the fact that the most exciting time of her life might be behind her.

"If you look at the things that have made everything so exciting, one, that pace of life was sort of unsustainable. So that's one sort of running off of adrenaline every day, that's exciting. The actual experiences, part of me thought, 'I met the queen, I met the pope, I was at Nelson Mandela's funeral, I've been on Charlie Rose -- what is there left?"