Who is Gillian Teys or Nell Grahame Clarence from A Great Deliverance and what is their importance?

Gillian is Tessa's daughter. She is described as a tiny, blonde haired, and youthful.... a young woman who is complacent in her role as wife and compliant with the expectations of others. She is married to a minister and daily tries to conquer the effects of being molested by her father as a child.