Niala had seen someone who had a lot of anger and hatred in them coming after Amaranth: she hadn't seen the actual threat that they posed but it was there nonetheless and she wasn't going to stand for it. No one attacked her daughter and got away with it. No. One. No one even threatened her little girl and got away with it. Of course, she could be over-reacting to the whole situation, but she'd rather over-react than under-react.
Sunset Island was within sight in less than a second....