Why is Meg the most suitable person to go to Camazotz?

When Charles Wallace is left behind on Camazotz under the power of the evil IT, Meg realizes that she is the most suitable person to try to retrieve him and bring him back home. This is because she knows him better than anyone else and also because she has been to Camazotz. Her father has been gone so long that he and Charles Wallace don't really know each other anymore. Calvin only recently became involved with the Murry family, so he hasn't had enough time to get to know Charles Wallace all that well either. Meg, therefore, is the one person left with knowledge of Camzotz who is close to Charles Wallace. Charles Wallace also understands her well. If anyone is going to be able to break through IT's mind control to reach the real Charles Wallace, Meg has the best chance. As she says:

it has to be me. It can't be anyone else. I don't understand Charles, but he understands me. I'm the one who's closest to him. Father's been away for so long, since Charles Wallace was a baby. They don't know each other. And Calvin's only known Charles for such a little time.