As for my wife, she is also a very devote Buddhist, now practising shurangama. But somehow the enmity she and mother have is so deep. She hate my mother so much.
We are sorry about your family situation.
Perhaps you should understand that is their mutual karmic retribution, not to mention yours as well.
At times, one must realize that there is only so much one can do, it does not hurt to go to a competent temple to ask for help to alleviate the karmic retributions of all the people involved.