Mama's Baby, Carlton's Maybe - S3-E5
Question: Cindy seemed fine with the Banks' wanting a paternity test, but Carlton later reveals that he is a virgin. So what exactly was Cindy planning to do? The test would reveal that Carlton was not her son's father, and she would need to admit to the Banks that she lied. Why stay there and wait for a negative test?
Answer: Cindy was taking advantage of Carlton. He had liked her for years and his parents are wealthy. She wanted to persuade him to marry her and raise the child as his own, no matter what his parents said about the paternity test.
Answer: The major plot point was Carlton was willing to let his family believe he was the father rather than admit he was a virgin. As long as he kept lying about not being a virgin, Cindy wouldn't necessarily have to lie, she could just claim she wasn't sure and thought it was Carlton's.
Bishop73
Also, her parents had kicked her out of their home. If nothing else, the DNA test would give her an excuse to stay with the Banks family for a few days.
Azalea