@Charlie74, I have many thoughts in response to your story. Feel free to mull them over and disregard as necessary
1. I think that 12 years has passed and a lot can change in 12 years.
2. I think that both you and she are probably very different people from what you both were back then.
3. I think that with the benefit of hindsight perhaps your friend already knows how unreasonable she was to you all those years ago, and that perhaps that is what has prompted her to now extend the olive branch.
4. I think it was very brave of your friend to make contact again after all this time, especially in light of the fact that she more than likely harbors regrets about her behavior towards you.
5. I think that no matter what happens you probably need to go gently with your response, as no-one likes rejection and the hurt it brings with it.
6. I think that people drift in and out of our lives for a reason, and the Universe has connected the two of you again for a purpose. It may be that is to simply heal old wounds, or it may be to renew your friendship.
7. I tend to agree with you that sometimes you have to step up and be the bigger person. I am very much someone who does not hesitate to cut off contact with people who are not good for me, and am reluctant to forgive and forget. I've probably lost a lot of friendships because of it too.
8. I myself sent a message on FB a few months ago to a young lady I had a falling out with many, many years ago. It took several months for her to respond to my message and accept my friend request - to the point where I had let it go and accepted it was not going to happen. We are slowly rebuilding our friendship now, which deteriorated in the first place due to a huge misunderstanding. I am so grateful she was able to see past that and give our friendship a second chance
As I said, take from all that what you will hon. It's just my perspective and of course you have to do what you feel comfortable with