By Robin Rieger

COLLINGSWOOD, NJ (CBS) – When the Collingswood High School Class of 2012 crosses the stage to get diplomas Tuesday night, students celebrating four years of hard work will be joined by a former student whose cap bears a 2011 tassel.

“I’m very excited to be able to have this opportunity to do this,” says Marie Fowler, of Oaklyn.

“I think it’s like a right of passage; she has to go up and get that,” her mom, Tracy Fowler, says.

Nineteen-year-old Marie Fowler was invited to walk in 2012 after a heartbreaking and life-threatening diagnosis the day before her graduation last year had doctors prohibiting her participation.

“They said, ‘You’re positive for leukemia.’ I just started crying,” Fowler remembers.

The news hit her twin sister, Michelle, just as hard.

“I don’t know what I would do without her,” Michelle says.

Michelle had to walk alone at graduation, but she brought Marie’s cap, gown and diploma to the hospital, where her sister’s treatments had already begun.

“They started IV’s…I needed blood. They did a bone marrow biopsy, which was tough,” Marie says.

All year–except in surgery–Marie wore her class ring. She accepted losing her hair to chemo, but she never considered losing her future to cancer. She’s now in remission.

“I planned on going to Camden County College for two years then transferring to Rutgers. It’s still my plan, just set back a little,” Fowler says.

Students at Collingswood learned plenty of lessons in math and science and English from their teachers, but they learned one very important life lesson from someone their own age.

“It says something about her. She’s a really strong person, and I take away a lot from that,” says friend Nicole Hall.

“The fact that this young lady has been able to handle this and fight through it is such an inspiration,” agrees Principal Edward Hill, who extended the invite to Marie.

“You never know what’s going to happen…don’t take life for granted,” Marie Fowler advises.

It’s the most important lesson she’s learned.