I totally agree with this being a great accountability place. I also wanted to throw out a couple of other thoughts:
1. A lot of people do really well with just writing down what they ate each day. I personally have done a system where I make a plan the night before for the next day and then report the actuals the following evening and repeat. There is something about having to write down what you ate that might give you just that moment to stop and think that you obviously were able to do before. The other piece of that was the planning. I do not plan to the calorie but if I have a plan of what I'm going to do, no matter how loose, it seems to be enough to make me take that moment again to think about whether I'm going to veer from the plan and many, many times I won't but if I don't have a plan, I tend to get pretty carried away.
2. I have read studies about how friends and associates can influence things like weight so that is not a figment of your imagination.

I really, really struggle in some social situations with certain friends BUT have found that many welcome my suggestions to do something a little healthier food wise or activity wise. Go ahead and make the suggestion and see what happens. Things like "How about if we go to Whole Foods for lunch?" allows you healthier choices that are easier to make if you can get her to buy into it. You aren't asking her to eat that way, just making it easier for yourself.
I'm really sorry about the depression. Been there, done that and HATE the t-shirt. I'm not sure from your post if you are in treatment but if you are, this might be something to discuss with the doctor also just so they know that you have noticed and it bothers you. There is some taboo stuff going on in the medical world around weight conversations so you might have to bring it up yourself so they know it is a safe topic for you (if indeed it is).
Peg