I struggle with emotional eating too. I don't think will power is all of the answer...changing habits is a big part as well. You are sad and looking for comfort. So you eat. What other things are comforting to you? Yoga? A hot bath? A massage? A walk with a furry or two legged friend? A call to your mom, sister, or close friend? Listening to a certain kind of music? The idea is to find something else to take comfort in, and do that rather than eating. It's different for everyone, but try to think of a few things that genuinely make you feel good, and do that next time you're tempted to eat out of emotion. If none of those work, maybe you could find a friend who is willing to be your ear and call them to talk about what is bothering you, or just journal when you feel that urge to eat. Sometimes if you get out what you're feeling the urge to eat will go away.

That's a horrible thing to go through. Yes, fixing food for your friend is a wonderful and natural thing for you to do. There's nothing wrong with that. Being there, a shoulder to cry on, bearing their burdens is one of the best ways you can show you care. Just make sure you aren't giving yourself permission to start binging because of this.
As far as other triggers that cause emotional eating, you need to recognize the underlying causes and begin to deal with these, one at a time. The ones you have control over first, especially. Some things are triggered by others, such as those brought on by abusive relationships, narcissistic or emotional terrorists, alcoholism, drug abuse and the like. If this is the case, I highly suggest finding a local A.A. chapter. They usually hold Alanon groups, a support group for people whose family members are dealing with addiction issues. They have really good books that teach you how to take care of yourself, and how not the enable the addict. If you are dealing with addiction to drugs/alcohol, jiin AA. Work throuh the steps and gain strength to do better every day.