How to block internet access at certain times?

my sister and I share a room and my sister is on the internet all night on school nights and never gets up in the morning, and I can't sleep because I have to listen to her IMs and her Annoying music, and I constantly tell my mom about this and she says she will Block it but she hasn't done it yet so I deiced to figure it out on my own so does anyone know how to block internet access at certain times like 5pm-7am or something?