Ashley was genuinely shocked to see Amaira, she was sure Taranis used his magic to send her outside the darkness, so what was she still doing here?
She recalled Taranis doing the same thing for her and she ended up back in the darkness. As she watched the two argue, she wondered, if Amaira wanted to stay in the darkness similarly to how she wanted to.
The thought made Ashley angry, she immediately thought Amaira wanted to stay in the darkness just to steal Taranis from her, even after she hurt him by falling in love with his brother.
Taranis told her he wasn't angry or sad because he fell in love with someone else too and was unfaithful to her. Ashley admired his selflessness, but couldn't accept his lack of resentment for his brother and Amaira, so she filled her heart with hatred for the both of them, on his behalf.