Betty's sister, Sue, was her best friend and confidant. They shared all their secrets.
Sue was the only one in Betty's family that knew about her relationship with Quinn and the truth about Andy.
Andy was not David's son. Betty started dating David as soon as she knew she was pregnant and told him the baby was his. David never questioned the fact.
In reality, Andy's father was an older foreign man, Betty had met at a bar. It was a one night stand and Betty never saw the man again.
Sue knew Betty was still in love with Quinn.