This is probably very irrelevant to the main story plot but I have a theory on Amy.

This is actually thought of by my friend who is obsessed with BTS. 

She thinks that Amy likes BTS.

In Neverseen, the fourth book, Sophie describes Tam and Linh as K-Pop idols.

In the eighth book, Legacy, when they go to Amy's room to return Sophie and Amy's memories, Sophie sees posters on the wall. 

She describes the people on the poster to look like Tam. This is why my friend thinks Amy is a BTS fan.