What is the most important event in "Torn Thread"?

There are a number of important events in “Torn Thread,” but I would venture to suggest that the most important one of all concerns Eva’s decision not to escape the labor camp with Kayla and a few other girls but to stay behind and care for her older sister Rachel.
Kayla is older than both Eva and Rachel. She’s also much worldlier, more politically aware. Having already experienced the horrors of Auschwitz, she’s under no illusions about the fate that the Nazis have in store for the Jews of occupied Europe.
She admires the Czech partisans for standing up to their German overlords and has been working with them in the shipping room at the factory. They plan to add chemicals to the fabric they are forced to make for German army uniforms so that they will quickly disintegrate.
But Eva wants no part of it. She simply wants to survive and by doing so help Rachel to survive too. Her decision to stay behind in the camp is hugely significant for a number of reasons. First of all, it demonstrates arguably the most important element in the story: the incredible bond of sisterhood between Eva and Rachel, which nothing, not even the most inhuman, degrading treatment imaginable, can break.
It also demonstrates her unshakeable faith in God. Despite the unimaginable suffering she and the other slave laborers have to endure on a daily basis, Eva remains a committed and (where possible) observant Jew.
In staying true to her sister and her God, Eva is also honoring the memory of her father. For just before they part for the last time, Eva’s father makes her promise that she will do everything she possibly can to help Rachel survive. He also urges her to trust in God. And so Eva makes the choice to stay; in doing so, she forces us to consider how the bonds of family and religion transcend the evils of this world and can never truly perish.