How can a woman who strangled her disabled daughter 29 years ago due to psychological pressures repent, and is qisas or diyya required of her, or is forgiveness sufficient?

A person who wrongfully kills another is subject to two rights: a right belonging to Allah, from which one is absolved through sincere repentance, and a right belonging to the victim's guardians, from which one is absolved by enabling them to exercise their right (retribution or blood money) or by their forgiveness. The mother is not killed for [killing] her child, according to the majority of scholars, due to the Prophet's (peace be upon him) saying: "A parent is not killed for [killing] his child," and the mother is like the parent in this regard. The killing mother must repent, resolve not to return [to such a sin], and seek absolution from the victim's guardians through blood money or forgiveness.