According to her father, Valena informed him that the arlessa was hiding things from the Arl and perhaps she was even involved in blood magic. She also thought that Isolde had an affair with the tutor of her son, Jowan.
Valena can be encountered by the Warden in Redcliffe Castle where she barricaded herself in a storage room. Valena says that first the Arl became sick and they arrested someone for poisoning him. Then some started fighting each other and afterwards the corpses appeared. They didn't attack the survivors unless they tried to flee the castle. So Valena managed to remain alive by hiding and waiting in the castle. She also informs the Warden that the arlessa is in the hall of the Castle, with her son, Connor.
Afterwards, Valena flees from the castle. The Lost in the Castle quest will be activated if it wasn't acquired by Owen. She can be found again in the Blacksmith's Store, where she will be thankful to her savior.
If her father is alive, he will also reward the Warden with the Shielded Dwarven Armor for rescuing his daughter. If Owen is dead, Valena will claim that she has no reason to stay in Redcliffe any longer and she will move to her aunt in Killarney. Furthermore, her fate is unknown if she isn't rescued before the situation with Connor is dealt with.