Friend is being blackmailed with nude pics, even some of when she was a minor..
This could (depending on the country) be a very serious crime, so I'd say report this to the police.
She is.. But I doubt they will do anything.. .
I also doubt they would do anything but reporting to the police or relevant authorities might really be important, even if not for anything but for reference purposes, as no one knows who the person is or what their next move would be.