What can a girl do who has been subjected to rape and harassment by her brother, along with threats of murder if she tells her family, and who fears the wrath of her Lord if she commits suicide?

Incest is one of the most heinous acts and the gravest form of adultery in terms of sin.

It is necessary to be firm with the aggressor brother and threaten him with informing those who can deter him or the responsible authorities. If the threat is not enough, then it is necessary to take effective measures to protect oneself from his threat of murder.

Wishing for death is forbidden in Islam, except for a strong overriding interest, and suicide is a disease, not a cure.

It is necessary to be patient and turn to Allah with supplication for his guidance and repentance, and for protection from his evil, while seeking help through the well-known supplication: "O Allah, we ask You to restrain them by their necks, and we seek refuge in You from their evils."