After Traveling Through Time and Becoming a Palace Maid, I Changed the Queen's Fate

A modern girl who is familiar with the ending of old history transforms into a little palace maid who can be sacrificed at any time; at first she just wants to avoid the death in the history books, but then she saves people who should have died time and time again. In the end, she discovers that what really needs to be changed is not a person's life, but the rules that determine who deserves to live.