What does the end bit, "her Bill abated but in 1657 the people listed above exhibited a Bill of Revivor" mean?
An action at law becomes inoperative (abates) when the plaintiff dies.
However, in this case, Mary AUSTIN's executors have revived the legal action by exhibiting a Bill of Revivor.
This (most likely) would have contained largely the same information and allegations as Mary's original Bill, but with the executors/co-heirs named as the plaintiffs and with extra statements to show that they were Mary's true legal executors.
Any relevant actions which had occurred in the case since the original Bill would have also been added to bring it up-to-date.