Is my brother's wife obligated to spend her postpartum period (nifas) in my mother's house after her death, based on my mother's will, which was witnessed?

If the house is owned by the mother, then her bequest of usufruct is permissible according to the majority of jurists, and its value is considered from one-third of the estate. Whatever exceeds this one-third requires the permission of the heirs. The heirs must execute a confirmed bequest, and whoever alters it is sinful.