Can't get over it.

About a year and a half ago, me and a friend who I care deeply for got into a fight of which we haven't talked since. Should mention she and I work at the same place. We said rather nasty things about each other, but the problem lies in that the reason we haven't spoken since was what other people have said since from what I've heard that I've got a posse. I don't. I was mad for a bit, but want nothing more than to resolve the situation, and have my friend back. I have no idea what steps to take from here. It's been almost a year and a half, and I still think about this horrible situation every day. She was my best friend that I've ever had, and I guess I don't know how to let go. There were romantic feelings on both sides, but never ventured by the way(she had a boyfriend). What can I do?