Is it permissible for a wealthy woman who has only one sick daughter to write all her wealth in her daughter's name, knowing that she has no siblings other than nephews?

If the woman intended, by writing down her wealth for her daughter, to transfer ownership to her after her death, then this is a will to an heir, which is impermissible unless all adult, sane heirs agree to it. However, if she intended to transfer ownership of the wealth to the daughter during the mother's lifetime and health, such that the daughter disposes of it immediately, then this is a permissible gift, and the mother is not obligated to gift anything to her brother's children, unless the intent of the gift was to deprive them of their inheritance. If the mother gifted her wealth to her daughter while she had cancer and then died, this gift takes the ruling of a will and is not enforceable without the heirs' consent. It is permissible for a person to divide their wealth among their heirs according to their prescribed shares, but it is better not to divide one's wealth during one's lifetime and to leave it according to Allah's ordinances.