YA book where grandfather says his newborn granddaughter is too perfect until he see a mole on her foot

I'm positive this scene is near the end of the book. The MC is being told how when she was newborn her grandfather said 'Nope, take her back. She's too perfect and perfect people are never happy.' Then he sees a mole on her foot and that's enough of a flaw. It's meant to be a sweet memory.