What should the questioner do, having caused discord among her family members after relaying something she heard, and now feeling remorse and fear of God?

It is not permissible to eavesdrop on others' conversations. If the grandmother and the uncle's wife, based on mere suspicion, accuse and slander others for taking money without proof, then they have committed a sin. It is forbidden to transmit words between people for gossip, unless there is an overwhelming legitimate benefit. Quarrelling with one's grandmother is a grave matter. It is advisable to counsel her with wisdom, not harshness. Grandfathers and grandmothers are akin to fathers and mothers in terms of dutifulness. It is recommended to strive for reconciliation and to mend relations between people.