Lisa looked at Vale's back as he entered the second floor of the Library… She felt that Vale had changed a lot after his battle against the Slender Zombie.
She felt worried about his mental health but she also has plenty of other things to worry about so she could only support Vale with little things she could do as a member of the Library Committee.
She had truly done her best searching for clues about the immortals that Vale had mentioned, however, aside from the children's fairytale books, she didn't find any other clues.
She could also suggest to Vale about the Chuch Libraries but he should also be aware that it's almost impossible to enter their library unless he decided to get baptized by the church. In the end, she can only tell Vale to try the second floor of the Academy's library.