I feel Nadia Russ's Art (NeoPopRealism) is "Contemporary Fine Art" and Zentangle is just a "Graphic Design".
Her work of arts are influencing to other artist is great thing, but taking idea from her and re-branding it without her permission is not at all a good practice legally or morally.
"Imagination is more important than knowledge." Albert Einstein.
R. Gopakumar 07.12.2011