Is it permissible to implement the grandmother's will to divide her jewelry among her granddaughters, and is this jewelry considered permissible for them, given that the granddaughters are not among the grandmother's heirs, and the jewelry constitutes her entire estate, and a will for a non-heir may not exceed one-third?

If the grandmother divided the jewelry among you during her lifetime—and she was not suffering from a death-threatening illness—and she died before you took possession of it, then the gift is void, and the jewelry must be returned to the heirs. However, if you took possession of the jewelry, then the gift is valid.

But if the grandmother was suffering from a death-threatening illness, then the gift takes the ruling of a bequest. A bequest to a non-heir, provided it does not exceed one-third of the estate, is valid. If the bequest exceeds one-third, only the one-third is executed, and anything beyond that depends on the heirs' approval, based on the Prophet's (peace be upon him) saying: "One-third, and one-third is much," and his saying: "Indeed, Allah has bestowed upon you a charity with one-third of your wealth at your death."

So, if you and your sisters are not heirs, and the jewelry constitutes the grandmother's entire estate, then you are only entitled to one-third of the jewelry, and the remainder belongs to the heirs, unless they agree to validate the entire bequest.