I think everyone makes fair points on here, I mean I'm 17, so I'm that sort of age where I'm in between both sides of the equation here, but I think that she should be given a reason as to why she is being told not to do it, but then, you should always respect what your parents want whether you think it is right or not, fair enough argue your case if you wish, but don't shout or make it in a disrespectful way, just try to explain your reasoning, cause chances are if you go behind her back or get annoyed at her, it will show you aren't mature enough to have a reasonable conversation about it, nor are you mature enough to understand why she feels that way.