Today is LILY 's mum's birthday , that reason she is not in her consciousness at all, her mind is just wandering with thoughts about her mum.
LIAM: hi
LILY: hi
LIAM: what you gonna sing today?
LILY: connected from Barbie and the diamond castle.
LIAM : ok Barbie girl, go on
LILY used to sing this song with her mum always , so while singing she was in tears (which no one could notice) and she was immersed in moments she spent with her mum, due to this her voice faltered n cracked.