All good points by Volt. You can also invest about $80 in a decent router. I currently have the Dlink dir655 and it has some really great features like access control (disable specific websites access) and web filters. Another thing is you can have MSN chat snooper setup that has her chats emailed to you every day. Lots of stuff that can help. A stealth logger would also work as you can install it without the user knowing. For this I would recommend Spector Pro, a little pricey but worth it. Can also be freely found on Newsgroups/Torrents. Check out the software available:
http://monitoring-software-review.toptenreviews.com/