Does her trait work with man thing and Howard the duck duo fig?

It doesn't. The character must be named "Man Thing."

Great piece, never lets me down.

I'd like to know, if I place the token over Hindering terrain, will it be count as hindering terrain as well?

I would say yes. If you put it on Elevated Terrain, it wouldn't become grounded terrain, right? The inherent characteristic of the terrain is not changed by the Special Terrain marker. Hindering remains hindering, water remains water, elevated remains elevated, and so on.