Why was Kristi sent to bed before Aunt Birtes funeral

Mama claims to have a aunt who passes away in Chapter 8. However, Great-Aunt Birte does not really exist. Mama and Uncle Henrik make her up so that they can hold a funeral, which is really an excuse for Uncle Henrik to collect all the Jewish refugees at his home before smuggling them to Sweden.This would happen late into the night so Kristi was sent to bed.

Since Kirsti didn't know it was a lie, mama was scared Kirsti would freak out there was a dead body in the house, or because she is too young and not mature enough to know what's going on.