Names were a mess in those years in Sweden, with the patronymic system being phased out, people picking new surnames as they pleased - and not least picking completely new names upon emigration.
The Find a Grave memorial for her father is more enlightening (to me). Looks like Floodberg for Brita was a first married name - she was born Jansdotter (patronymic) in Brunskog parish. She did not marry in Sweden.
But since I'm not thonning, I'll leave this to somebody who is.