Finding Peace?

Lately, I've been battling a personal battle with a certain someone and events took place two months ago that apparently, to this day, still have a miserable effect on me. All I can do is ignore it...for now. How do you find peace with yourself when the problem will virtually always be apart of your life? How do you move on and create happiness when the problem will always come showing up, creating havoc? I'm not one to hold grudges, I'm a peace maker, I'm a lover, I'm the type to forgive easily and move on. However, this ONE person, has shown me a whole new side to what I'm capable of feeling and it absolutely, without a doubt...sucks. I've let this person get the best of me and for some reason it's holding me down. I can't shake it.

I've been through some horrific, miserable things in my life and I've always learned to cope and forgive the people who have wronged me. I moved on. So, why can't I move on with this person? It really has been eating at me and has turned me into this negative person. If you know me, you know that I'm not negative. You know that I like to be optimistic and find ways to look for the happiness in little things. I'm still that person but at the same time, I have to work harder every day to be happy with myself. It's never taken this much work. I don't hold people responsible for my happiness, so why can't I just forget about this person and move on? Why does this person have this effect on me and why do I allow her (oops, cat's out of the bag) to continue to dig her nails into my skin and wound me?

I refuse to talk to this person b/c nothing I say (nor what anyone says) will make a difference. This person is in her own world and has created this delusion/illusion that she is of no fault of anything that she has done to other people, including myself. Knowing this, I should just accept that she'll never change and that obviously the only solution is to cut her out of my life, as I have done for the past 2 months BUT even doing so, something about her just gets under my skin. Hearing her in conversation makes me cringe, makes me mad. Receiving random text messages from her, trying to guilt trip me, send me into a stressed state of mind.

What is a person to do? How do I find peace with this?
Realize, that most of my questions are rhetorical. I needed to write about this b/c I can't get it off my mind.