Easy solution, if you want to stay away from wireless, would be connect one cable from your router to your xbox, then another cable from the router to one of these plugged into the wall;

http://www.homeplugs.co.uk/

Plug another into a plug outlet on the kitchen and connect to the laptop with ethernet cable.

Voila. Your xbox connected to the internet 24/7, and her laptop connected 24/7, and you can both go on at the same time. Sorted. And no running hugen lengths of cable round the gaff! I was gonna do the same thing, but then about 15meters of cat5 for free so didn't bother