Forgiveness is like the dropped stitch. If it's not fixed immediately, the hole of bitterness gets bigger and bigger. Jesus said people would suffer as He suffered for His name.
Although Rivka teaches others, we see that she also struggles with sin. No one is perfect. Everyone needs Jesus.
Responding to others as Paul teaches in the New Testiment to respond is a choice. Only in relying on the Spirit can that choice be made. And the choice has to be made despite how others are responding. The other person involved might not apologize. And they may never actually accept your apology. But their reaction shouldn't affect our ability to forgive and ask for forgiveness.