My sister Sue died of bone cancer when she was just 57 years old.

That was more than three years ago. And while I've written memorials for my mother, my father — even my cat — I still haven't been able to write a single word about my sister Sue.

I would like to be able to tie up all the loose ends and create a nice neat package that would make sense of her difficult life and untimely death. But Sue's life was neither logical nor predictable.

The truth is, I never really knew my sister Sue. She was the designated black sheep of our family. I was never anything but pale gray by comparison.

Headstrong, drop-dead gorgeous, wildly intelligent, she was Odile to my sister Evy's Odette. Evy was the fair-haired homecoming queen, the good girl who had to work hard to make the honor role. Susie had a sky-high IQ and didn't give a hang about her grades.

In fairness to Sue, she got off to a bad start. When the doctor delivered her into my mother's arms on September 13, 1946, my mother's response was, "Well, she's cute, but she's not mine!"

The McDonald girls were born fair-skinned and bald with big blue eyes. That thick dark hair, those dimples — she wasn't one of us!

Ironically, it was Sue who ended up looking the most like my mother of anyone in the family.

The photo at right shows Sue with her high school boyfriend, Rob Muir.

We all liked Rob, but after graduation, Sue followed Frankie to Denver, and then moved to Florida with Evy. She eventually landed a job as a secretary at Cape Canaveral (now the Kennedy Space Center) in Titusville.

She picked up extra cash working as a go-go dancer. Frankie used to drive down from Jacksonville to watch her dance.

"She was very popular, and I was always so proud to say that I was her sister," says Frankie, "but she was so good looking that I sure felt like a wallflower by comparison!

At NASA, Sue met and married Al, an engineer with Latex International, the company that designed space suits for the astronauts.

Sue and Al lived what seemed like a charmed life, jet-setting to ski in the Swiss Alps or the Colorado Rockies. Sue began acquiring an impressive collection of Indian jewelry.

During these years Sue was a nationally ranked downhill skier. I remember photos of her, hiking in the Alps in a stars-and-stripes bikini with her skis over her shoulder.

Frankie remembers going to Houston for the Apollo 14 splashdown. Several astronauts greeted Sue by name as they walked down the hall at the Holiday Inn. While Susie and Frankie were having a drink at the bar, several reporters gathered around the table just to "drink to her beauty".

"Sue was dressed in a one-piece brown velvet jumpsuit," says Frankie, "and I remember her saying that was her "otter" suit." (The otter was Sue's totem.)

Al was transferred to Houston and then Wilmington, Delaware. Sue found the only job she ever really loved, working as an assistant to an archaeologist for the state of Delaware.

Somewhere along the way, their marriage fell apart.

Sue's next husband was as unlike Al as possible. Jerry the truckdriver took Sue's name when they got married, but neither the name nor the marriage stuck.

I visited Sue in Delaware several times and watched in awe as she seduced her handsome French travel agent with the speed of a cheetah. So I breathed a sigh of relief when she began courting Jesse, a soft-spoken tax attorney with a Wilmington law firm.

I organized their wedding in Morrisville, Vermont, hippie style with a contra dance band in a field next to the converted barn where my boyfriend lived.

They seemed happy, and a few years later they realized their dream of moving to the mountains near Asheville, North Carolina.

For reasons I still don't understand, their dream quickly became a nightmare. When Sue and Jesse came to Vermont for a family reunion in 1985, the strain was obvious. Glass in hand, Sue threw me out of my house. Years would pass before I understood that she was drunk at the time, and even more years before I realized that she was an alcoholic.

Neither Sue or Jesse found steady work in North Carolina. Sue tried to start a word processing business, but ended up spending most of her time researching our family's genealogy. When she was diagnosed with Type II diabetes, she became an expert on the subject and a major contributor to online diabetes support groups.

Sue and Jesse parted company and Sue sank further into Appalachia, eventually taking up with another trucker — ironically named "Al" — who walked straight off the set of "Deliverance".

She eventually got her own commercial license, and they drove together for awhile, but it was a difficult and dangerous life, and Sue's health continued to deteriorate.

Sue dated a guy in his 70s for a while, but came to the 1990 family reunion in Daytona Beach, Florida, with a fellow who was just 19 (and looked 15). Even then, in her 50s and packing a lot of extra weight, Sue still turned heads.

"Do you remember the reunion in Florida when one of the doors needed fixing"? Jan wonders. "After the two guys left I asked, 'Did anyone give those guys a tip?', and Susie replied, 'No, but I let them look down my front!'" Jan says, "I'm the sister who has to tip".

Family reunions aren't the same without Sue. We didn't realize, until she was gone, how much of the fun we had together was just talking about Sue. She was the most naturally witty person I ever met, and she could light up a room with her smile.

It was Sue who coached me on how to change my diet when I was diagnosed with Type II diabetes. And Sue who figured out that my charismatic, crazy husband suffered from borderline personality disorder. And who promptly offered to shoot him.

"I don't know how to get rid of anything I can't shoot," she quipped.

In 1999, Rob Muir looked her up on classmates.com. Sue and Rob met in New Orleans — they hadn't seen each other in 34 years. Rob was disentangling himself from a long, unhappy marriage, and Sue was a breath of fresh air.

Finally, it seemed like Sue might have the kind of life she deserved. Sue joined Rob in Arizona, and they were married November 24, 2001, in Bayard, New Mexico.

The cancer showed up as a pain in her hip at a family reunion in Tucson in 2003. By the time it was diagnosed, it had already spread to her bones.

Right: Sue with Tramp the Dog.

Her doctor gave her between six weeks and three months to live. Strong as she was, she toughed it out for almost another year, declining the the indignity of chemo or radiation treatments since the bone cancer was inevitably fatal. Being sickly wasn't her style.

She kept her family at a distance during her illness, which made her decline and death even harder to accept.

I kept a few pieces of Sue's jewelry, and distributed the rest to my girlfriends. My friend Kathy swears that guys hit on her every time she wears her "Sue" earrings!

And so Sue's mojo lives on, but so does the yawning gap between what her life should have been, and what it was.

My sister Ruth is more philosophical. Quoting from, "Mayflies and the Metasequoia Tree," by Stanley M. Aronson, M.D.:

Nature dispenses longevity in a seemingly random manner. For the mayfly, life is measured in hours, while for the metasequoia tree, it is measured in centuries. The metasequoia has a stoical life, steady and measured in its growth, tempered only by wind and lightning; it dies after more than a millennium, probably of utter boredom. The mayfly lives its brief earthly stay in full and unfettered ecstasy — smiling, no doubt, each precious minute of its fragile existence.

"This is an analogy for my relationship with Susie," says Ruth. "I spent countless hours worrying about the way she jumped into life feet first, and I tried to give her the benefit of my own cautious, sensible approach!"

"Of course, she nearly always chose the opposite direction. In doing so, she enriched my own life in countless ways. I miss her every day."

Left: Rob and Sue at a Diamondbacks game in Phoenix, May, 2004.