My wife’s sister has asked my wife to assist her in writing the will but we also found out that she wants it hidden from her husband. In other words, her husband should not find out what is written on the will. Two questions:
(1) Is that OK to hide wills from the spouse? Or should it be shared?
(2) Should my wife assist her or not, knowing fully well that this is not known to her husband.

1- It is her right to do so.
2- No problem in assisting her