These are not only a word but then, for me, she is a girl with a lot of secrets and keeps them to herself. She only tells them to others only when she is really forced to do it. For example, at the book no 24 File 10, she only told Kudo that the apo at the apotoxin 4869 stands for apoptosis that means programed cell death only when she thought that she was about to get killed by Gin . Talking about Gin, earlier at File 7, she only told Kudo that the real codename of Melkior is Gin even though she has known Kudo for quite some time.
So, this is why for me, she is a girl with lots of secrets but it is normal as Vermouth usually says that< secrets make a woman a woman>...