Ashley Hegi, seen in her yearbook photo, was three weeks away from her high school graduation. (CBC)

A southern Alberta community is remembering a girl described by teachers as a four-foot-tall teen with a 10-foot-high attitude who defied the odds of a rare genetic disease that causes premature aging.

Ashley Hegi, 17, was one of 53 people in the world — and three in Canada — with Hutchinson-Gilford Progeria Syndrome. There is no known cure, and most children with the condition usually die around age 13.

Hegi, who lived in Coalhurst about 200 kilometres southeast of Calgary, was admitted to a Lethbridge hospital on Friday. She died on Tuesday, one month before her 18th birthday and three weeks before her high school graduation.

But friends at Coalhurst High School said it wasn't Hegi's condition that made her stand out.

"When you talked to Ashley, you didn't think about her being sick; you just thought about how wonderful she was," said friend Lais Morrow on Thursday. "I don't know how she'd gone through everything she'd gone through and not been bitter at all, like that we ever saw at least."

Hegi made it her mission to teach the world about her condition by appearing in documentaries and media reports. Her mother, Lori, also maintained a web page that followed their lives.

At 14, Hegi reached out to others with progeria in a YouTube video, in which she advised them, "When somebody stares at you, don't let it bother you because maybe they don't know about progeria. You can tell those people about progeria. Maybe they'll understand. And if they don't, it's OK. You're one of a kind."

Ashley Hegi and her mother Lori appeared in documentaries and media reports to raise awareness of Progeria.

Teacher Deb Woodcock likes to borrow a saying that one of her colleagues coined to describe Hegi:

"She had a four-foot stature and a 10-foot attitude. And that just summed her up.

"She taught us far more than we ever taught her, just as far as the amount she was facing in her life and how she just took it all in stride, and the rest of us kind of struggled through our struggles, and if we put it all in perspective, we learned a lot from her."

Hegi volunteered at an animal hospital and was a season ticket-holder for the Lethbridge Hurricanes hockey team.

"The thing about Ashley is, [she had] no time for a pity party. She lived life to the fullest," said the team's general manager, Roy Stasiuk.

A funeral service will be held Saturday at the Evangelical Free Church in Lethbridge. Hegi's family asks that memorial donations be made to the Progeria Research Foundation.