It might be helpful to show her the prayer used by the Priest during Confession, part of which is:
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"My spiritual child, who has confessed to my humble self, I, humble and a sinner, have no power on earth to forgive sins, but God alone; yet through that divinely spoken word which came to the Apostles after the Resurrection of our Lord Jesus Christ, saying: Whoever sins they remit, they are remitted, and whoever. sins we retain, they are retained, we too are emboldened to say: Whatever you have said to my most humble self, and whatever you have not succeeded in saying, either through ignorance, or through forgetfulness, Whatever it may be: God forgive you in this present world, and in that which is to come."