You are not the artist of this piece. Take it down or you will be reported as an art thief. It doesn't matter that you credit the original owner; you are posting it without permission under your own name with absolutely no artistic input.
Honestly, I don't think she haves permission but she gave credit to Kawiku. This is not art thief, she gave credit, she never said it was hers. This is clled reposting . I actually find it senseless and useless, but you can't blame her for anything.
This is an art website. If you don't make it, you don't post it. Not following those rules is art theft, whether or not you credit the artist. Unless she has a signed document stating that she has permission to post the work and that there is no copyright, it's stealing. And she is still posting something under her username that isn't hers. And what's the point? Why would someone just post work that isn't their's on an ART WEBSITE?