Jenna Bush stepped to the podium, looking poised in a floral print dress with gentle earth tones. But she couldn't quite hide the butterflies as she stood before an eager bookstore crowd to introduce her book, "Ana's Story: A Journey of Hope."

"This is my first day, so I'm a little nervous," the 25-year-old first daughter said, laughing softly.

Her face lit up, though, as soon as she started talking about the subject of her nonfiction narrative, a teenage mother from Latin America who was born with HIV.

"Ana changed my life. She's only 17 years old, but she's lived the life of somebody so much older," Bush said. "Despite her hardships, Ana is so much like the teenagers here in the United States. She reminds me of myself at that age."

During President Bush's 6 1/2 years in the White House, his daughters — Jenna and her twin sister, Barbara — have done their best to insulate themselves from scrutiny. It hasn't always been successful, as when they were famously cited for underage drinking. Jenna also stuck out her tongue at photographers during her father's re-election campaign.

The resulting image was of the first daughters as irresponsible party girls who stirred memories of their father's youthful misbehavior.

But that's changing now. While Barbara, who works at the Cooper-Hewitt National Design Museum in New York, maintains a low profile, Jenna has begun to reveal her passion for education and helping the underprivileged. She taught elementary grades at a charter school in Washington, D.C. before going to Central and South America as an intern for UNICEF.

If her work as a writer makes people realize she's more than a social butterfly, Jenna is fine with that. But she wasn't too worried to begin with.

"The people that know me and love me, my students and colleagues, never had that perception of me," she told The Associated Press in a brief interview before her reading of "Ana's Story" at a Borders bookstore in Annapolis.

While she hasn't done many interviews, Bush spoke with confidence — if sometimes so quickly that her words got ahead of her intended meaning. She said she never felt the need to interact with the media until she had something important to say.

"I didn't really have a reason," she said. "I didn't have something that I was passionate about."

Now she does. Looking back, she's amazed at how quickly "Ana's Story" came together. She saw the potential in the teenager as soon as she saw her last fall at a community meeting for women and children living with HIV and AIDS. (Ana's name was changed to protect her privacy, and Bush does not reveal which country she lives in beyond saying it's in Central America.)

Bush began meeting with Ana several times a week, speaking with her — entirely in Spanish — about her difficult upbringing.

Ana was infected with HIV by her mother, and both of her parents died of AIDS. She was raised by relatives who beat her and was molested by her grandmother's boyfriend. She ended up in a juvenile detention facility after running away from home. She became pregnant by her first boyfriend, who was also HIV-positive.

Bush was struck, though, by Ana's positive outlook. She was vigilant about taking her medication and did not pass on the virus to her daughter, and she recently returned to school.

By the time Bush went home for the holidays last December, she had written several sample chapters and began shopping around her book proposal. She wrote most of "Ana's Story" between January and April, working with editors at HarperCollins over e-mail. The book runs nearly 300 pages, but it's written in simple language directed at teenage readers.

The chapters are short, sometimes no more than a paragraph, and the book includes dozens of color photographs taken by Bush's close friend, Mia Baxter, who also interned with UNICEF. Portions of the proceeds will go to UNICEF.

Bush said she started by writing longer, more conventional chapters, but "it just really was too much. It was too heavy, and I thought kids would find it really grueling and not at all optimistic or fun to read."

Several people in the audience said they admired the president's daughter for educating children about such difficult subject matter.

"What she's doing is a humanitarian effort that crosses political lines. It helps people to see her in a different light — different than some of the bad press she's gotten in the past," said Angela Patterson, 46, sitting next to her daughter, Lyndsay, 13. "It's hard to live your life under a microscope. She's obviously matured."

Another part of that maturation: getting engaged in August to her longtime boyfriend, Henry Hager. Bush wore a sparkling diamond-and-sapphire engagement ring but said wedding plans are on hold while she tours the nation for the next two months.

"Hopefully in January we can sit down and talk about it," she said about the wedding. Asked if she might be married at the White House, the first daughter said, "Right now, anything's possible."