Yvonne first appears when Dot and Shirley Carter text her from her son Charlie's mobile phone and arrange to meet at Dot's house. They meet, and Yvonne and Dot immediately clash, but later get on. She confirms that Charlie is her and Dot's son Nick's son, after Dot believed that Charlie was lying to her about his identity. When Charlie and Yvonne leave, it is clear that something is suspicious as Charlie asks whether Dot believed what Yvonne has said. They also imply that Yvonne has been hurt by a member of Dot's family.
no did know up by Nick Cotton while still very young, and her subsequent abandonment by him, has left Yvonne bitter with the hand she’s been dealt… and she’s not above taking that bitterness out on others. A strong and upstanding Catholic, Yvonne is known on occasion to use her faith to mask her own shrewdly observed judgements of others.
Since Nick left Yvonne’s whole world has centered around Charlie - and their relationship has become unhealthy, insular and controlling. Yvonne’s greatest fear in life is losing her son… so God help anyone who tries to take him away from her...