That's against the law in Canada if you don't give her the 'go' to send it. I would suggesting filing a police report.

That is illegal as hell. Call the police, file charges for taking video footage without consent and distributing footage without consent.

This would be illegal for a guy & it's just as illegal for a girl. You can't make her friends unsee what they have seen but you can demand that they delete every copy and involve the police if they don't comply.

As far as I understand it, OP being underage wouldn't have any repercussions for themself unless they were either under the minimal age of consent, in which case it COULD get their parents in trouble for not providing a safe environment or they sent nudes to the girl. If the only exchange of nude/sexual content was the girl sending the video to her friends, she and her friends would be the ones in legal trouble, for the video content without consent, video distribution without consent, and distribution of child pornographic consent. So as long as OP was in the clear on those fronts, the only thing them being a minor would do is make their case have more severe repercussions for girl- unless there is some nuance to the usual laws in OP's region. Even then, it would quite likely be worth it to report her anyway- she would definitely come out worse once all charges were compiled, especially since, if OP has sent prior nudes, she would have been likely to have distributed those. And each instance of a distributed photo would be an individual charge of child pornography in most locations. That is, of course, assuming that OP IS underage.