If we think about it, she's an 8yo who worked for every type of people, so she must have developed an eye for people who can be trusted.
And more, she's a child... They say that children are very sensitive for this kind of thing.
@Mariartis maybe she has a plan to prevent her death when the family notice what happened.
I think she's probably going to run away in a few chapters... There is no way she will stay in the house.