Is it permissible for a Muslim woman to inherit from her unbelieving mother, and can she ask her mother to bequeath all her possessions to her to prevent Western authorities from seizing them?

It is permissible for a Muslim to ask their non-Muslim relative to bequeath one-third of their estate to them. The permissibility of a non-Muslim bequeathing all of their wealth to a Muslim is based on the validity of a non-Muslim's will for more than one-third, which varies according to the non-Muslim's place of residence and their heirs:

A non-Muslim in a land of Islam with their heirs residing there: Their will for more than one-third is not enforceable unless the heirs consent. A non-Muslim in a land of disbelief (at war with Muslims): It is permissible for them to bequeath all of their wealth, because the restriction on a will for more than one-third is for the right of the heirs, and the right of the heirs of a non-Muslim at war is not observed.

If the wife is a recent convert to Islam and there is a fear that she might be alienated from the religion if she does not inherit from her mother, then it is permissible to act upon the opinion of those who allow a Muslim to inherit from a non-Muslim, as this serves to win her heart over to Islam.