Has the former fiancée who called caused the divorce of her former fiancé from his wife, or is what she is experiencing merely a delusion?

You made a mistake by calling this young man, because such calls between a girl and young men are impermissible, as they are a gateway to temptation and evil. You must repent to Allah and abide by His limits, and not pay attention to whispers [of Shaytan] but rather turn away from them. Among the things that will help you get rid of them is seeking Allah's help and making abundant supplication.