Is a woman sinful if she gifts money inherited from her husband to her sister's son and daughter whom she raised, given the presence of well-off brothers and sisters and the woman having no children of her own?

There is no sin or blame on a woman for donating as much of her money as she wishes to whomever she wishes, even if the recipient is wealthy. This act of donation is enforceable and cannot be revoked if the conditions for enforceability are met: maturity, freedom, full mental capacity, and attainment of رشْد (sound judgment). However, the intent behind this donation must not be to disinherit heirs.