Flaws in Fanfics Percy Jackson Edition

Judgement #5

Erin was terrified and confused. They had no idea what was going on,

They?

they looked at their dad, to see him trying to stand up. They noticed blood starting to appear on his shirt, and was scared. They didn't know what to do. All they knew was they had to live, but if they ran now, they'd be followed.

They?

Their dad noticed this, so he yelled. The words he said were impossible to make out, but they caught the attention of the creatures. "You damn Cerastes! You impossible creatures! Pay attention to me!" He continued to yell, distracting the Cerastes from their original target. He looked at his child, and mouthed "I love you" before the serpant-like creatures wrapped themselves around him slowly, about to suffocate him and make him into a shish kabob

BRUH

Erin closed their eyes, taking in a sharp breath, before turning around and running out of the house

Do you mind explaining why Erin is referred to as a multi entity