Answer:
I can infer that Jess and Layla's friendship is very close. On page 5 its states, "...and Jess was a Leo, just like Layla. Their birthdays were two days apart, and their mothers had met in the hospital; they had been best friends ever since." The text also mentions, " 'Jess.' she whispered to her best friend, 'I think I am allergic to science.' Jess peered at Layla through her bangs and sighed. 'Layla, you can't be allergic to a subject.'" Here, it shows us that they are talking nonsense between each other, which is sometimes things that best friends do. Especially in class.
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