Maybe not blackmail, per se.
DWS knows that Awan knows everything about the DNC server “hack” and about her communications to the DNC from her iPad.
He knows that Seth Rich stole the emails and sent them to WikiLeaks.
And he knows what DWS decided to do about that.
This is why DWS is sh!tting bricks!
I don’t think it originated as blackmail, but that may well have been part of the result, years along the path.
Especially when (1) the Awans get desperate, and (2) they have been seeing and accumulating so much sensitive PERSONAL as well as Democratic Party, governmental, and national security info for so long.