My 'friend' is trying to control my life

I've mistakenly confided in this girl about having mild depression a while ago and shes completely gone behind my back and told a few people, called me depressing etc, bitched about me and made these few people think im some manic depressive psycho who can dampen anyone's mood. which is not true. She's also incredibly bossy and controlling over everything i do and to make matters worse, in a few months she is going to be one of my flatmates, which means she will try and control the house, the food (which i am not happy about since i have disordered eating and want to lose weight which she will jealously try and disallow as she is already envious of my weight loss which she cannot match) . Argh she is just trying to control everything and to be honest i want to become as detached from her as possible, but i don't know how? Any help on this? or anyone had to deal with anyone similar?