So IMDb can either be very right sometimes, or very wrong. It depends on your perspective, and also just until someone making the movie can confirm or deny this certain rumor/news.
Well IMDb now lists Kat Dennings as Darcy / Hela, which is intriguing. Kat certainly seems to look the role and I think she may be capable of playing it as well.
I like the idea of maybe having one of the villains in this (Hela in this case) being thrown down to Earth and making a fake name for herself (Darcy). It gives Thor somewhat of a counterpart in the film, but not so much?
Who knows, maybe Jaimie Alexander can Tweet whether or not this is concrete? :D