Well they have to be kept secret. Most secrets are kept for good reasons, and if they have to be kept they will, but you have to do more than just not say anything about it you have to act it, fake it, try to make everyone else believe everything is just fine. It affecting liesel is probably really high, she has many secrets already, she keeps stolen books, a jew, stolen food. It was torturer Hans to have Max leave because his secret wasn’t safe anymore. Rosa has changed from yelling at everything to a calm-ish person, because of keeping Max hidden.