Yes you could use the right kind of router (or install an open source firmware like http://www.dd-wrt.com on your existing router if it supports it) to either throttle her bandwidth or do traffic shaping to make sure the packets you are interested in get handled first.
Or you could set up OpenDNS so you can see her surfing habits. Has potential for blackmail.
Or you could set up a linux box running as the router and do even more fun stuff like examining exactly what sites she goes to, read her IMs and emails, etc.. Or mess with the websites like having all the images display upside down or replacing all the ads with hard core porn ads.
