If you bought it on DVD it would come through the post and which would be easier for them to find out. Also, it would come up on recently watched on Netflix. You best bet is this. It comes into your email and no one would even know. Plus ITS 2018. They're not the ones watching it, so if you want to see it, freakin watch it gal!! I understand if it's not your bank account but if it is and in your name, due to data protection, it is against the law for your parents to see anything in your bank or read your bank statements. Sending my love and hope you can watch :)