How can one help a grandmother who was a folk singer and is now bedridden and understands nothing, and she doesn't mention God but rather repeats folk songs, keeping in mind that she was not advised to repent in the past?

All praise is due to Allah, who has blessed you with the grace of repentance and guidance. If the woman has become confused and lost her mind, then the pen has been lifted from her until she regains consciousness, based on the saying of the Prophet, peace and blessings be upon him: "The pen has been lifted from three: from the sleeper until he awakens, from the child until he reaches puberty, and from the insane person until he regains his sanity." If she regains consciousness, then she must repent for what she did before her confusion.

If she has wealth, its zakat (definition) is due. If the obligation of Hajj was established upon her before she lost her mind, then Hajj must be performed on her behalf from her estate if she passes away.

Your righteous supplications for her benefit, asking Allah to forgive her, overlook her misdeeds, and free her from the Fire, will benefit her. You may also give charity on her behalf, or establish endowments whose reward will return to her, such as printing religious books, digging wells, building mosques, and sponsoring orphans.

It may be that the madness that afflicted her is an expiation for her sins and an erasing of her transgressions. We ask Allah to forgive her and accept your kindness towards her in this state, for it is a means for you to enter Paradise. The Prophet, peace and blessings be upon him, said: "May his nose be rubbed in the dust, may his nose be rubbed in the dust, may his nose be rubbed in the dust." It was asked, "Who, O Messenger of Allah?" He said, "He who reaches old age with one or both of his parents and does not enter Paradise." And Allah knows best.