ANSWER:

Whether you are sinful or not, this is related to whether you were negligent or not and whether you knew something like that could have happened or not. 

Either way, repent to Allah and cut commutations with such an evil friend.

QUESTION: My friend is refusing to remove a video of me from the internet. It was at her wedding and us friends were casually dancing but I had no idea it was being recorded or that it would be published online. When i found out later on i regretted & asked her to have it removed but she refused. Am i sinful?