Not the bride's fault OR the bridesmaids' fault. Maybe the bridesmaids could file a class-action lawsuit against the former groom? Of course I have a feeling that will cost more than the $100 still remaining on the tab.
I don't recall the OP mentioning the groom cheating, so a class action lawsuit may not be a good idea.
In fact, I know of a situation of where the wedding was called off because the bride slept with the best man AND one of the groomsmen. Since this bride gave no explanation in her text it might be a bit premature to assume the reason for the cancellation was the groom cheating. SHE may have been responsible for the wedding being called off...