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.. .
Nowadays cyber crime is spreading and police is also working very hard to solve the cases. In this situation it will be the best way if you report it to the police. Also you may try to hire ethical hacker from freelance marketplace if possible.