Personally, I don't know much about the hardware end of things except that you can probably manage to burn up your laptop or explode your batteries if you do something wrong.
Anyway, maybe this will help: http://www.instructables.com/id/Increase-...
1) You can block his IP with a firewall.
2) The phone company can (and will if her guardian request it) block his phone #.
3) Put a logger on her PC to monitor communications with him.
4) Have the phone company give you a log of her calls to make ...