What is the ruling on money and profits deposited in a state-affiliated savings account, and is it obligatory to return all previous money and profits, or does repentance make what preceded permissible?

You must abandon the forbidden transaction, regret it, resolve not to return to it, and seek forgiveness. This is the meaning of repentance. The same applies to your mother; explain to her the obligation of repentance. As for benefiting from interest acquired before knowing its prohibition, some scholars deem it permissible, citing the verse: "So whoever receives an admonition from his Lord and desists, he may have what has passed, and his affair is entrusted to Allah." As for interest you acquired after knowing its prohibition, you must dispose of it by giving it to the poor and needy or for public welfare. The same applies to your mother.