What to do when you become the "bad" roomate?

I just started my first year of college in september. At first I was living with 3 girls but then one of them moved out. Because of cultural reasons and age difference (they were of the same background and both quite older than me) made a decision and moved out and into one of my friends dorms. At that point me and M were really close and we worked like clockwork, always communicaing our issues, and enjoying rooming with each other. I went from being a complete utter slob (LoL) to actually regularly cleaning my stuff, and becoming more self-conscious abot my surroundings, while she went from neatfreakiness to...well normal-ness.lol. It was really alright, but then her bf created a rift between us and i kinda did some things I regret, like eating some of her private stash of hot chocolate, m&m's and swedish fish.(lol..i'm a candy addict)and reading her emails. I really want to make things right, but I'm afraid it's too late, and seems like I cannot do n e thing to change how she feels.