Guest post by "Gelliebean" I think this is a good thing for Sarah's own sake. Forgiving someone doesn't mean you have to forget everything they've done to you and pretend there's a clean slate, or give them opportunities to hurt you again; but it does give you the chance to let go of anger and resentment, and stop it from eating you up.
I love that she is compassionate enough to tell Penny "I forgive you," and smart enough to know they aren't magic words that automatically fix everything.