Who is rachel in the chrysalids?

In the beginning of the book, David says how him and a group of people are all telepaths. Rachel is one of the telepaths.

the other telepaths are;

-David

-Rosalind

-Michael

-Sally

-Katherine

-Anne

-Mark

and later on in the book David finds out that Petra (his little sister) is also a telepath.

Hope this helped in some way..=)