In A Wrinkle in Time by Madeleine L'Engle, what does Meg have to do break the spell of the dark thing?

Meg has learned that she cannot break IT’s power over Charles Wallace by mere brute force. This has a limited effect on Charles Wallace, breaking his concentration for only a minute. She remembers that Mrs. Whatsit gave her the gift of her faults, so she tries to figure out how her flaws can help her in this situation. Her impatience has made her persistent, willing to return to Camazotz to rescue Charles Wallace, even though her father is close to giving up. It is the simple yet complicated act of loving Charles Wallace that rescues him. Meg realizes that this is the one thing that IT cannot understand, the unselfishness of love toward someone else. It has tried to spread “peace” by convincing everyone on Camazotz to be “like” everyone else. There is peace through “uniformity.” Yet it is not the same. Similarity is not the same as being identical. It is through the uniqueness of love for the flaws in ourselves and our self-sacrifice for someone else that can overcome evil.