It is unclear how she met Robert or when their affair began. Robert loved her so much that he planned to leave his wife, Maryse, for her. However, it became apparent that Maryse was pregnant with their third child, so he stayed. A grief-stricken Maryse told her daughter, Isabelle, about the affair around six years later. While Isabelle did not know who Annamarie was, she still greatly resented her for nearly wrecking her family.
During a trip to the Adamant Citadel, Isabelle asked Jocelyn if she knew her. Initially refusing, Jocelyn eventually obliged and told her Annamarie's name and the fate she ultimately faced in the war. Isabelle stated that she had never even heard of Annamarie before, and was dismayed to realize that knowing who she was did not make her feel better.
While the affair remained known only to a few people for a long time, Isabelle blurted it out to her brother Alec Lightwood, and a few spectators, during an argument with Robert in Alicante in 2007.