Also, a friend of mine had a pretty intriguing theory afterward. Maybe this is common knowledge/speculation, but...
Eliza's given last name was Esposito (an Argentinian name by way of Italy) and the creature came from South America. Because of that connection, my buddy was saying that the scratches on her neck might not have been just scars that the creature turned into gills, but could have been actual, dormant gills, and the creature essentially "activated" them in the end. In other words, Eliza, an orphan, may have actually been a descendant of one of the creatures, or was the result of a human/creature hybrid, hence her mute-ness. And she was basically returning "home" in the end.
Eliza's given last name was Esposito (an Argentinian name by way of Italy) and the creature came from South America. Because of that connection, my buddy was saying that the scratches on her neck might not have been just scars that the creature turned into gills, but could have been actual, dormant gills, and the creature essentially "activated" them in the end. In other words, Eliza, an orphan, may have actually been a descendant of one of the creatures, or was the result of a human/creature hybrid, hence her mute-ness. And she was basically returning "home" in the end.