Unfortunately I've been in this situation before when I was younger and I've been the one that didn't speak up when something was bothering me. Don't take her being mean to you as something you've done to deserve it. She could be upset at herself for letting things go the way the did and it comes out this way. If it has taken her this long to decide to call off the wedding, take this as her final decision and move on. I would be thankful that she didn't stay with you longer, after you got married, while still deciding if you were right for her or not.
When she says you should have picked up on her detaching herself.. that is BS! She took the easy way out - not dealing with issues as they came up, and just calling it quits.
Be thankful that she told you now and you didn't end up marrying her.