Is it permissible to give the needy sister from the remaining portions of a vow, and is that considered fulfilling the vow?

The vow must be fulfilled in the manner in which its owner vowed it. It is not permissible to give the value of the remaining sheep; rather, it is obligatory to give the eight sheep. If the intention was to slaughter and distribute them, then that is what must be done. But if the intention was merely to give them away, then it is sufficient to give them or some of them to the brother-in-law (husband of the sister) for him to benefit from them or to undertake their sale.