Go to http://blackmailscams.com
and follow the advice as if she was a blackmail scammer.
It was most likely just someone fooling around online,,,but better be safe than sorry.
Blackmail scammers and other scammers are everywhere on every social site platform and breeding like cockroaches, so be extremely careful about adding any stranger to any personal profile you have in the future, and never get naked online. I think you realize what could happen now.
Since she has not asked for money yet, there is no need to go to the police at this point.
If a video shows up online or she somehow finds you and threatens, then by all means report the scam to the police.