Claire's fear of Daniel casts an sinister light on whatever happened, as it begins to show that it wasn't just a benign accident. The fact that she's willing to talk to Tom and trust him with this information shows that, despite his closeness with his brother, Tom is likely someone trustworthy and also not angry, scary, or vindictive like Daniel. This starts to show the reader that Tom has an identity separate from Daniel, even if Tom might not see it that way.