Is the compensation money obtained from an accident caused by the deceased herself permissible or impermissible? And is it permissible to take it with the intention of donating it if the siblings insist on taking it?

If you know the mother is at fault, it is not permissible to file a case against an unknown party in order to fraudulently obtain compensation. Therefore, it is unlawful to take money resulting from such an act, as you have no rightful claim to it, in accordance with Allah's saying: "O you who have believed, do not consume one another's properties unlawfully" (Quran 4:29). Consuming unlawful earnings has severe consequences, including the non-acceptance of supplications, as stated in the noble hadith: "And his food is unlawful, his drink is unlawful, and he is nourished by what is unlawful; so how can his supplication be accepted?" Furthermore, consuming unlawful earnings affects the heart, as its corruption is linked to the corruption of the entire body, as the Prophet, peace and blessings be upon him, indicated in the hadith of Nu'man ibn Bashir: "Indeed, there is a piece of flesh in the body; if it is sound, the whole body is sound."