Valeria is a resident of Burgh de Rott, a small town in southern Morytania. To access Burgh de Rott you need to complete In Aid of the Myreque. She may be found alongside Ivan in the house just west of Marius and Gabriela.
She disappears after The Branches of Darkmeyer the day after Catalina goes missing, causing Amelia to note that like Marius, she too has gone missing. A missing person poster for her appears on the western wall of the Burgh De Rott bank, which reads "Missing: Valeria - gone, just like Gabriela and Marius."
She appears again during River of Blood near the end of the quest, being one of the vyrewatch who revert back to human form when crossing the newly blessed Salve River.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!