She is a human who carries the bacteria 'anthorax' and she can't die from it, thus why her name is Anthrax. She can mold it into whatever she wants it to look like, and she can spread it to anyone, unless the person is immune (which is very unlikely). The teal colour in the animation is the anthorax being molded. It looks pretty but it isn't.

Btw the lyrics are from here https://www.youtube.com/watch?v=uCi8x4HQDEg