Could use your advice

I'm experiencing a bit of an off topic dilemma and have so many emotions swirling I thought I'd share it and see what your objective opinion might be. Any advice much appreciated.

Once upon a time Jack and I had a couple friend we were very close to. We knew the hubby, A, for years before he married Z, and he would come over our house for dinner all the time and we adored him. Then he married Z and she was just as awesome as A, and the four of us hung out all the time. We had other friends in common but the common denominator was the four of us. Z became my closest girlfriend. Closer still, because the four of us connected so well, they felt like family away from family. My parents knew them, asked after them. I knew her folks and when they were visiting we'd often go over because it was like seeing relatives. Z and I went shopping together, had lunch together regularly, talked on the phone almost every night and we hung out every weekend whether just the four of us or with larger groups of people. We referred to each other as sisters. I could confide anything in her and I knew that no matter what happened she would always be there for me.

Except she wasn't. One day, three years ago, out of nowhere, after I threw her a surprise birthday party, she stopped speaking to me. She stopped returning my calls. She blocked me on facebook. When I saw her she would turn around and walk away. I was shocked. I tried approaching her when I saw her to ask her what happened but she said she didn't want to talk to me. I later learned from friends that she had ripped up photos of us and one was stuck on her fridge torn in half. I had no idea what I did. I grieved that friendship like someone might grieve losing a long-time boyfriend for no reason. I was devastated. Jack and I were both shocked and stunned.

I was the quieter more introverted of the two of us so she took over all my prior friendships. I no longer felt welcome to attend events of mutual friends. In the three years since I had to rebuild almost my entire social circle. I now have other friends and they're very nice but I never had the type of friendship I had with Z ever again. Despite what she did I missed having that sisterhood feeling with someone. Knowing that I could call someone at 3am and they would be there for me. I really really missed it despite not wanting to.

In the years that passed she got pregnant and had a baby girl who is a few months old now. July 2009, when she was pregnant she e-mailed me after two years of silence to wish me a happy anniversary. I was confused and simply responded with a terse thanks.

Her husband and Jack still play on the same flag football team and a few weeks ago he asked Jack to have lunch with him. He told Jack that he misses our friendship a lot and that he never found friends like us again. After all this time he finally told us why Z ended the friendship: She thought we were too close and it was impinging on her ability to expand her social circle. That was why she ended our friendship. She certainly did expand her social circle. There's hardly a person I meet who doesn't know Z (she's very loud and funny). I still don't know why she had to end our friendship to get this- but that was her choice. Her husband told Jack she regrets what she did and they miss us. Jack shrugged his shoulders, what is there to say really?

Today, 2.5 years after she ended our friendship, I got an e-mail from her. She apologized profusely for what she did and that she thinks of me every day. She said she thought of me as a sister and she lives with regret for having treated me as she did. She hurts knowing I'm having a baby and that we can't raise them together like we would have. She said I was her first true friend so she didn't appreciate its value and now over the years she's learned that friends like me are hard to find and she fucked up a really good thing. She said she knew we can't fix the friendship we had and she has no expectations of a response from me but she hopes I can empathize with her.

I'm so confused. I will be seeing her at a wedding in two weeks. This thought was already filling me with dread because I hate having to see her but now she's reached out and I dont know what to do. I bawled my eyes out reading it because despite all these years I never made another friend like that again. Though I know I'm not missing who she is, to this day I miss the friendship that was.

Jack got angry reading the e-mail. He said she wants to unburden herself because she feels guilty for what she did. He told me not to respond and just to accept this apology as closure to a very painful part of my life. I mean, this may sound really dramatic, but she broke my heart and he had to see me lose all my friends because of her actions.

Do you have any advice about what you would do if you were in my shoes? Part of me wants to ingore her reaching out. Part of me wants to write back and say thanks, keep it short and sweet. Part of me wants to approach her at the wedding in two weeks to talk (except I did that in the past and she snubbed me so I feel uncomfortable with that), and part of me wants to get coffee with her and talk and at least become cordial again... and then, I admit there's a part of me that wishes so so badly that we could erase the years and I could have the friend I had, the friend I never found again.