How to end a friendship??

ok, so I got this friend, we've been best friends, in fact inseparatble since last january. Weve dated twice and me and her have worked p it. We've had major hits in our friendship over the past year dealing with her trying to make me jeoulous, telling me who I can or cant be friends with, and telling me that I cant be friends with basically everyone that I've been best friends with for over 5 years. I feel really close to her and all and for that reason she knows things that I cant afford to let get out. Now, after constantly having the same conversation about me hanging out with this girl caylee, I know I dont want to continue in this relationship, dispite being so close, Ive know ive wanted out for months, i mean i care about her alot, but I cant be friends with someone that controls every aspect of my life, and ive tried talking to her multiple times, but now shes going overboard, shes dating my best friend of 8 years, shes felling on me constantly, sending mixed signals, yelling at me everyday just because I hugged some girl or something. To her, it seems I can only talk to one person - her, but she can talk to how ever many people she wants and im not allowed to get mad. She even hates me talking to my own sister who is the closest person to me in my life. But my fear is that now that she knows nearly every one of my secrets, and all shes going to do what shes done in the past - start rumors, and talking **** about me all over school. I cant afford that and I need to know what I should do to end things on a healthy note, and clean and without her talking ****. *ps. shes has amitted to being in love with me several times with dosnt help matters.