I use to work / live with this family for 18 months almost two years ago.
We always had such a great relationship until the last couple of months we had a massive argument and tried to be civilized with each other, but there was no denying that serious damage was done with what was said. The day I moved out she was not home and I left her a gift and a heart felt letter. I thought that surely she would have contacted me in some way, she has all my details, to say something about the letter or gift or something, but alas no word from her until yesterday when she found me on another website and sent me a message saying how she misses me so much and that she would like to visit me... sounding as if nothing ever happened between us. I have not answered her as I truly do not know what to say to her. I still cannot forget about how bad she made me feel when she said those things she said before I moved out. It is nice to hear from her, but I feel that this is a part of my life that I have closed the chapter on. What do I say to her as to why I never invited her to my wedding? I just don't know what to do.

I guess, in the end it is your choice, but sometimes it is good to put old disagreements aside and behave with dignity and maturity.

Perhaps you can let her know that it's lovely to hear from her and that you're glad to have this opportunity to put aside any old differences. I would be up front about the disagreement, rather than igoring it, but act as if it is something in the past, that has been resolved.

You can then let her know that many things have happened since you last spoke and tell her about the wedding. It might pay to be honest and just say that you felt awkward and given the circumstances of your departure didn't know how or if to invite her.

Her reaction will let you know if it's worth pursuing the friendship any further!

Good luck.

Thank you gem, your response is very much appreciated. Great answer!