Vanyel was Chosen by Yfandes after Tylendel threw himself off the tower, and Vanyel stumbled away. Once Vanyel collapsed, he felt Yfandes in his mind for the first time. Yfandes shielded Vanyel for some time while his mind and emotions were in turmoil, and his magic was out of control. Since Yfandes waited ten years to Choose, Heralds took Yfandes' Choosing a Herald to have a certain significance. Even Herald Mage Savil expressed surprised disbelief, as well as being deeply concerned about what the Choosing meant for both Yfandes and Vanyel.
Yfandes is known to be very caring and even protective at times of Vanyel, as is expected of Companions. In fact, the only sign other Heralds had of Yfandes' Choice was her fierce guarding of Vanyel, letting no one near him.
Little is known about Yfandes' previous life as a Herald, as all Heralds are offered choices at death: to come back as someone who will be Chosen, as a Companion, or to retire and go to the Havens. There are several brief moments where Vanyel catches a possible glimpse of Yfandes' previous life (as an image of a lady superimposed on Yfandes), but other than that, not even Vanyel knows who his Companion was.