this reminds me of the time when my mom took the cable that ran from the vcr to tv to stop us watching tv.
When she wasnt home, we would take the antenna cable and plug it straight to the tv,bypassing the vcr. By taking the cable from the vcr to the tv, all she did was stopping us from using the vcr.
if she is sufficiently informed,or persistent enough. She will be able to bypass all the measures you will take.She could,for example, use a live cd and that will bypass everything you installed on the computer.She could go online through her friend's computer across the street in some sort of a proxy server setup and that will most likely bypass everything you set up at the router level.
You are trying to solve a social problem using technical means. Those means are available and will be presented here but they can go so far in trying to solve the underlying social problem.