Nancy is the conniving, manipulating wife of Dr. Craig Wesley. She was determined to become Mrs. Chief-of-Staff, and she didn't want to marry Mike. She wanted to push Mike out of the position so her well-deserving husband could take over his rightful place.
In the beginning, Nancy was very much Daddy's little girl, constantly threatening Craig if he didn't become Chief of Staff, she'd leave, taking Daddy's money with her. Then she came into her own, scheming on her own and always loving her husband no matter what. With Craig, she planned for Mike to be found in a bad position with a woman at a party. Nancy began pushing Carrie with Mike, but became a confidant to Carrie also. She did have a heart. But she was in the middle of a breast cancer scare.
Nancy survived her cancer scare, and began pushing Craig to push Ali in her lawsuit against Mike Horton and the hospital. Nancy wanted Craig to be COS more than anything else. He got what he wanted, just in time for another strike to hit their relationship. Chloe Lane, a foster girl Nancy had brought home with her, was in actuality Nancy's daughter, that she had given up for adoption as a teenager. Despite Chloe and Craig both pressing her, Nancy refused to name Chloe's father.
Nancy eventually revealed that she had been raped at 16 by her father's business associate, Dr. Frederick Sykes, when it was revealed that Chloe had leukemia, and needed a bone marrow transplant. Brady and Craig were able to discover that Sykes was not, in fact, Chloe's father. Testing proved that Craig was really her father, which left Nancy wracked with guilt at the thought that she and Craig lost so many years with their daughter.
To provide Chloe with the best possible donor, Craig and Nancy decided to have another baby. Despite some health problems, Nancy was able to successfully conceive and carry their baby to term, and when the little girl was born, they named her Joy, because that was what she brought to them.