Is it permissible to cast a spell on the girl's mother to complete the marriage to her, with the consent of the girl and her brother, but the mother's refusal, knowing that her father is deceased?

It is impermissible, according to Islamic law, to resort to sorcerers to facilitate a marriage. Instead, strive in supplication (Du'a) and seek out the best times for it to be answered. Try to persuade the girl's mother through those close to her. If the mother insists on refusing without a valid Islamic reason, then the girl has the right to marry a suitable man, while still being dutiful to her mother.

If this marriage does not come to pass, do not despair. Put your trust in Allah and ask Him to provide you with another righteous woman, for: "And perhaps you dislike a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah knows, while you know not."

Know that guardianship over marriage (Wilayat al-Nikah) belongs to the male relatives ('Asabat) of the woman, and women do not have this right. Furthermore, excessively placing obstacles in the way of marriage is a serious matter that leads to widespread discord (fitnah) and corruption in society.