What sacrifice does Piper make for her father in this section?

Piper has always felt abandoned and unloved, so to find out that her father was actually trying to protect her and care for her all along is very comforting. She now feels that she needs to return his love and protection by helping him to forget the monsters. She knows that he will also forget that she is a hero, and she does not want to lose this new relationship of trust and respect that they have formed. However, she is willing to sacrifice this, the thing that she has always wanted, to give him a better life.