Tristan,
I just saw your message today. The figurative speech in your sentence, "If he was hurt, the cowardly worm, she just had to help him" is a metaphor.
When the author uses the phrase "the cowardly worm" to describe the hurt person, you and I both know that "he" is not actually shy invertebrate wriggling on the floor. A metaphor is a word or phrase used to describe something differently than it actually is.
For me, I get the image of a classic, second-class villain: an untrustworthy guy who is not brave enough to be accountable for their own actions.
That is the beauty of figurative speech. A good metaphor can bring a whole scene to mind, or invoke a strong emotion, in only a few short words.