What should the questioner do about her paternal uncles who mistreat her and her parents, after she stopped visiting them due due to the excessive abuse and backbiting, and they cut off relations with her because of that?

If the uncles were the ones who severed ties, then there is no sin upon the nephews. Care should be taken to maintain ties with them to the extent that no harm is incurred, and not to retaliate against them with a severance of ties. This is the most perfect state of maintaining kinship ties, as the Prophet, peace and blessings be upon him, said: "The one who maintains ties is not the one who reciprocates, but the one who maintains ties is he who, when his kinship ties are severed, he reconnects them." And if they initiate connection and kindness, they will have Allah's support against them.