"squirmed like snakes..."
See in text (Patterns)
The speaker uses this simile to describe her experience of shock and pain. The letters could “squirm like snakes” because they become blurred through her tears. They could also “squirm” because her disbelief or shock warps her vision of the world. If we compare the words to “snakes,” creatures used to symbolize evil and danger, this works to imbue readers with the speaker’s feeling of panic and foreboding.