Jenna Bush said her "boyfriend" — she doesn't like the word "fiance" — proposed after rousting her at 4 a.m. to go hiking on Cadillac Mountain in Acadia National Park in Maine.

"It's supposedly where the sun first hits the United States," President Bush's daughter said in a television interview about her recent engagement to her longtime boyfriend, Henry Hager.

"I did not want to go hiking at 4 in the morning," she said. "It was freezing. But we got up, and we hiked in the dark for an hour and a half, and then when we got towards the top, with the sunrise, he asked me."

In an interview that will be broadcast Friday on ABC News' "20/20," Jenna Bush, a 25-year-old elementary school teacher, described Hager as "smart," a "hard worker," "open-minded," "fun" and "very supportive."

Hager, 29, who has been a White House aide and worked on Bush's re-election campaign, will be returning to school this fall to complete his master's degree in business administration at the University of Virginia. He has an undergraduate degree from Wake Forest University.

"He's extremely outdoorsy," she said. "If he could spend every day outside, he would. He's very into the environment, and he was as a child. He hiked a lot. And so, now he's trying to find a job where he can support the environment and, and be outdoors."

Jenna Bush agreed to an interview with Diane Sawyer to promote her new book, "Ana's Story." The nonfiction book is based on the life of a 17-year-old Latin American mother infected with HIV. She met the mother while working for UNICEF, teaching in four countries in Latin America and the Caribbean.

"My job for UNICEF was to document the lives of kids living in exclusion, which means, you know, in extreme poverty, living with HIV AIDS, living in abusive households, kids that don't have access to school or medical care," she said.

On other issues, Jenna Bush ducked a question about whether she agreed with her father about the war in Iraq, but she said she understood critics who argue that she and her twin sister, Barbara, should serve in Iraq.

"Obviously I understand that question and see what the point of that question is for sure. I think there are many ways to serve your country. I think ... what's most appropriate for me to do is to teach or to work in UNICEF and represent our country in Latin America."

When asked who was the child in the White House she always thought she'd want to emulate, she replied Chelsea Clinton, the daughter of former President Clinton and Sen. Hillary Rodham Clinton, D-N.Y., a Democratic presidential candidate.

"I think Chelsea Clinton is, is very kind and, um, smart and articulate," she said.

"She's always been very friendly to us, but we just wanted to be ourselves, but she was, she's beautiful and poised all the time."