Hi devilishandsweet,
Don't be so hard on yourself! Its terrible that someone can be so cruel to you, especially as she is family and should try to support you, but you know what they say, 'you can't pick your family'. She is obviously not the most responsible person in the world from the sound of things, and certainly has no right to sit in judgement of you. Can you take her off facebook? She doesn't sound like someone you need in your life right now, whilst you may need to see her once in a while, it will minimise how much she can hurt you.
There is so much more to you than your weight, try to think of all the positive things in life you have going for you. I know its difficult when you have existing depression anyway, can make you so much more sensitive to criticism and really impact on your self esteem. Like you said yourself, you had been doing so well and had felt better in your mood. You are taking control of your weight, which is a huge part of who you are, that has taken some hard work and determination to get as far as you have. Its important to be able to recognise those achievements, she can't take that away from you.
As for the eating, it doesn't matter!!! There are going to be times in life, even when we get 'slim' when we may still comfort eat and have binges, especially if feeling down, one cake or a fast food mountain, the amounts are irrelevent. The important thing is to allow yourself to start again and move on from it, don't resign yourself to that being 'the end' and continuing to binge for another day, and another. You'll just perpetuate the cycle of feeling depressed, so eating, then feeling worse, and on it goes. You can have control over what you do from this day foreward, it takes enormous strength sometimes but i know you can do it. Believe in yourself!
As for having no 'go' in you, yes that goes hand in hand with feeling low, but don't underestimate the power of junk food! When i cheated last week physically i felt like ****, and i'd only had a few bits here and there, your body's probably feeling pretty freaked too, once you get back on plan, your energy should improve again.
Thinking of you hun, lecture over, sorry for going on, just don't want to see you throw all your hard work away over this. xx