I am so sorry to read this. It is very sad.
I think that something must be very wrong in your daughters feelings towards you and just wonder if there is anything at all that you can think of for this attitude on her part.
I would be so tempted to go to the church and see her but I do feel that it maybe very painful for you and may also cause a scene.
I agree with Archduke a letter would be a good idea. In your shoes I would be tempted to write her a letter and have it delivered by special delivery or something.
In it I would say that I had heard about her wedding and I was happy for her as she took this next step in life. I might also say I was very sad not to be invited but I would respect her wishes and not be there on her special day. I might also add that I would be thinking of her on her special day and that my love for her would always be there if she ever wished to contact me again.
If your friends and son have been invited I would hope they would take video footage on video camera or phone, and still pictures for you to see later.
I think your mother has behaved abominably and I am surprised in one sense you have not cut contact with her, but I know you cannot because it would further affect your daughters relationship with you.
I am really sorry to suggest this but is there any hurt or issue that she feels you did not protect her from or any thing connected to the anorexia where she blames you?
Anorexia is a mental illness and in one sense if your daughter has lived through that maybe cutting you out of her life has been a way to survive that in some strange way. I can't make sense of it because that is what mental health issues can sometimes do. But I do know that anxiety made me a bit crazy before I had CBT for it.
Can I really encourage you to get some counselling for this, for you, for the situation you are in.
"Should I just realise I have no daughter anymore?" No, I do not believe you should. She is still alive and in the world. Even those who have lost their children to death still consider themselves to be parents to those children. They will still say things like, 'I have three children but one is in heaven or one has died."
Maybe one day something will change, a family funeral or another wedding will bring her back to your door. Or maybe the birth of a baby will make her realise what she has lost.
I am so angry at your mother on your behalf, I really feel to come between a parent and their children is very evil. Just make sure you do not give her any ammunition to tell your daughter about! May your care of her be exemplary despite the fact that she has behaved so very badly.
If you do decide to write a letter, please do it soon so she has time to reconsider, and if she does, go slowly and not OTT. I feel very sorry you have been so badly treated.
I do hope and pray that there will be a change.