Explain to your fiance how you feel this was a breach of the trust you have in her - how does she react?

Sometimes people do things where they think they are being helpful. She likely has no real concept of "wanting nothing to do with your mom" and might have assumed you guys were just fighting - and that a wedding might be a great time to try and heal that... or maybe not...

I guess get some more info from your fiance and then proceed. If she is just showing a disregard for your feelings (intentionally) then yeah put the wedding on hold.

People of reddit like to view the world black and white - she did what? Ok that's a paddling!

Truth is there is no way you can elaborate in a post your relationship, how effectively you have communicated your back story to your fiance, etc.

tl;dr - give your fiance some room allowance for a lack of judgement and reaffirm your stance on this. If she completely understands why you don't BM in the picture and still disregards you, treat with the advice others have given about postponing the wedding.