I blame Charlotte for the jilt, not Miranda...
First of all, if Charlotte's klepto daughter hadn't stolen Carrie's phone the morning of the wedding, Big would have been able to talk Carrie and crisis averted. So, Charlotte, teach your daughter not to steal!
Second, it was Charlotte who stopped Big from apologizing to Carrie in the street. Maybe if he could have said what he wanted to say, they'd have driven back to the church together.
Thirdly, it was Charlotte who convinced Miranda not to say anything later that evening. If she had, maybe it all would have made sense to Carrie who may have called Big, etc.