Final answer:
Shelly believed that lice peeking had been killed due to a misunderstanding in a conversation about plants. The misunderstanding led to Shelly's belief that lice peeking had been killed.
Step-by-step explanation:
Shelly believed that lice peeking had been killed because she misunderstood the word 'lice' as 'plants' in a conversation with Claire.
Elizabeth assumed that Claire was removing lice from plants, but Claire actually meant she was putting lice on certain plants as a form of experiment.
The misunderstanding led to Shelly's belief that lice peeking had been killed.