Is it permissible for a twin sister to donate her eggs to her sister who suffers from leukemia and is unable to conceive?

It is impermissible to donate ova from a woman to be fertilized by the sperm of a man who is not her husband, even if the fertilized ovum is implanted in the womb of the donor's sister. Decision No. (16) of the Islamic Fiqh Academy explicitly prohibits fertilization between the husband's sperm and an ovum from a woman who is not his wife, followed by the implantation of that fertilized ovum in the wife's womb. Therefore, it is impermissible to donate ova to a sister. One should instead increase supplication and take all legitimate means.