Leah Siskin has told her little sister’s story many times, to many people, in many different ways. It is never easy.

One December evening, Leah wrote the words again, this time in a heartfelt message to friends, family and colleagues, asking them to honor her sister’s memory by supporting Leah’s team in the National Eating Disorders Association walk in Washington.

“On February 29, 2012, Sarah would have turned 28,” wrote Leah, my best friend since childhood.

Sarah, an exceptional student who dreamed of being a doctor, died nine years ago at 19, after a years-long battle with bulimia. Sarah’s death left her family a choice: succumb to sorrow, or forge lasting meaning from the loss.

Six years after Sarah died, her family asked me to share their story in a 2009 article in The Post. They hoped that it might help others. The response from readers was overwhelming.

There were letters from people who wrote about the struggles of friends and family members; from people who were motivated to seek help for the first time; from a woman whose son had an eating disorder; from parents of a daughter who died from the effects of bulimia the day the story was published.

The letters strengthened Leah’s desire to fight eating disorders.

In 2010, she started by talking to teenage students. Early last year, Leah learned that there would be an organized walk benefiting NEDA at the American University campus in February. It was only a week away, but Leah decided to try to pull together a last-minute team and hope for the best.

“We raised $5,100 in six days,” Leah said.

Some of Sarah’s friends walked with Leah and her family. The team, Sarah’s Squad, was so successful that Leah was asked to be on NEDA’s planning committee for this year’s walk.

On Feb. 19, Sarah’s Squad — bigger this year, with at least 25 walkers and a fundraising goal of $5,800 — will march again, this time on the Mall.

“The hope is that this will keep growing every year,” Leah said. “I don’t want any other family to have to go through this. If raising money for research and resources helps other families get their child what he or she needs, then that’s what we’re going to do.”