Yes, if she can be supported to tell her Mum in a quiet way (once Mum is home) it would help her to mature and also show her Mum that actually she can be trusted. She knows the code - so Mum hadn't been that careful about hiding it - did give in to temptation (understandable) but also realises she shouldn't have done it. It all sounds typical for her age. I think if I were you I would be asking for her assurance she won't access the series again while you are in charge, remind her that she is putting you in a very difficult position, that you want to support her but equally you were also given the same instruction about the series and that it is her Mum's decision to make. If you can just chat in a light way, rather than sound heavy handed, it should be fine. If for no other reason than with luck your granddaughter won't want you to be 'in trouble' with her Mum. I woner if there is peer pressure at work here, is it an 'all my friends watch it' belief? Peer pressure is a powerful thing. By telling you she knows the code your granddaughter seems to be testing her boundaries with you, best not to collude with her. Good luck!