After having gotten the man who is being threatened up on Lilan’s back, Erin is struck by an arrow. She threatens Lilan with the silent whistle to get Lilan to leave her behind. Lilan wouldn’t have left Erin otherwise, but by presenting herself as a threat, Erin can drive her off. Perhaps this final threat has completely destroyed the trust between them.
But Erin doesn’t mind destroying the trust and relationship she has with Lilan. She doesn’t believe she deserves to have a relationship with Lilan anymore. She believes she needs to drive Lilan away completely, because Lilan should not be near her, because she’s done something truly irredeemable as Lilan’s caretaker.
Erin wants to die and she believes if she dies, Lilan will truly be free. And she doesn’t want Lilan to feel anything about her passing.