"P.S. What I Didn't Say," an anthology just released by Seal Press, includes 36 unsent letters between female friends. Included in the collection is Susan Johnston's letter, "Watching You Waste Away," written to a friend who had bulimia.

L. and I became friends our senior year of college, at a time in our lives when strange eating habits seemed perfectly normal. She seemed like every other woman I knew in her early 20s; most of us subsisted on salads and worked out several times a week, but if we skipped a day on the cross-trainer or drank a few too many sugary cocktails, we hardly noticed. Most of the women I knew would roll their eyes at their reflection in the mirror and complain about "love handles" while squeezing into a size-six tank top.

I thought most women had a love/hate relationship with their weight, so I didn't think L. was especially troubled or unusual. Until we decided to become roommates.

Broken Body Image
The clues were there from the beginning, but it took me months to piece them together. Maybe she was good at making excuses. In high school, I'd already seen a close high school friend shrink to a size zero and nearly go into kidney failure in the process. Back then, I didn't know how to help her, and it had been unclear when her prom-dress diet crossed the line into dangerous territory.

But with L., things quickly became evident. On our first night in the new apartment, I offered to cook dinner for us, picturing the kind of friendly, domestic roommate relationship where we'd sip wine while cooking and dishing out advice on careers or dating, but she politely declined.

Later on, I invited her to a friend's potluck and she canceled at the last minute on the pretense that her sugar-free meringues fell flat. (There's a reason most pastry chefs use real sugar!) I told her no one would care if my dish was our contribution. But she said she was tired and stayed home.

The pattern continued, and because she seemed lonely and distant, I tried harder to bring her out of her shell. It didn't help.

The Case of the Missing Yogurt
A few months after we moved in together, I noticed food gradually disappearing from my shelves in the cupboard. At first, it was such a small quantity that I thought I was imagining it. Or that I'd eaten a little snack and forgotten. And I didn't want to quibble over a few dried cranberries or fat-free pretzels.

But then came the disappearance of a full pint of my Häagen-Dazs Dulce de Leche fat free frozen yogurt (OK, maybe I had food issues, too. But Häagen-Dazs fro-yo is really good.). I confronted her. She blamed it on the mouse who lived behind our stove.

"Don't eat my food!" I demanded. "And if you do, replace it!"

"I'll try," she answered timidly.

"Don't try," I snapped. "Just don't touch it."

The Road to Recovery
A few months later, when she admitted that she was bulimic, my words from our "yogurt fight" echoed in my guilty head. Why hadn't I said something more supportive? Had I unknowingly fueled her eating disorder with my own neuroses?

I told her I'd do anything I could to aid her recovery, so I hid the bathroom scale and my stash of women's magazines. I stopped making comments about my own body and bringing sweets into the apartment and started suggesting ways we could bond without food (walks, craft projects, movies).

Turns out, it wasn't up to me. Our friendship grew strained and distant, and she found a subletter and moved out of our apartment early to be with her family. Part of me was relieved, and another other part regretted that things hadn't worked out differently. Part of me thought that if I could just be a supportive, nonjudgmental friend, I could will her well again.

I just hope she knows that now, too.

Susan Johnston is a Boston-based writer/blogger who covers career and lifestyle topics. You can read her letter to L., and other unsent letters between female friends, in "P.S. What I Didn't Say," available now from Seal Press. For more information about bulimia and eating disorders, click here.