Is it permissible for sisters to retract their waiver of their share in the inheritance after the financial situation of the shop has improved, and what is required to be done regarding that?

The heir's relinquishment of their share of inheritance under duress or out of shyness does not make it permissible for the recipient, based on the hadith: "The property of a Muslim person is not lawful except with their willing consent." If the one relinquishing is a minor or mentally incompetent, their relinquishment is void. However, if she is an adult of sound judgment and relinquished voluntarily in exchange for an agreed-upon sum, and a long time has passed, she does not have the right to revoke it thereafter, even if there was an injustice involved. But for one who relinquished out of shyness and embarrassment, what was taken from her is not lawful for the one who took it, and her full right must be completed.