Karen said that she was going to be the villain so this seems like just a coincidence.
The sexiest thing about her is her voice (and temperament.), so what accent is she planning on using in this movie, no matter what character she is going to be playing.
Imagine if Death was Scottish?
(Imagine if Death wasn't Scottish?)
Although, the thing about Death in the Marvel Universe is that she is somewhat tight lipped, so Karen might not have any actual lines whatsoever despite being a very heavy figure in the line up. Although a really good sigh, or an eyeroll and even a tactical snort could be right in Karen's wheelhouse.
Besides, Death is beyond good and evil, so Villain doesn't fit here either.