5. I believe someone with disordered eating would be more likely to want to talk about eating disorders. In many cases, those who eat disorderly have no idea they themselves are on the brink of the different side of eating orders, and so don't associate any personal grief to the topic. Yet, people with eating disorders are more likely to be embarrassed or shameful of their enactment of such voluntary eating disorders which might have gotten out of hand.

6. This is a very delicate issue, and must therefore be brought up slowly in the event...

I would first casually bring it up just to get a reaction in order to collect a better understanding of how the issue should be approached. After it had been brought up in casual conversation with no personal allegations, I would take the person aside and confront them in a careful and understanding way.
References

Stoppler, Melissa Conrad. "Anorexia Nervosa." Medicinenet.com. 2008. Retrieved November 14, 2008 at http://www.medicinenet.com/anorexia_nervosa/article.htm.