offhand i can think of a few ways.
firstly software, there are many solutions available - google is your friend.
secondly set the link speed to half duplex - this essentially limits the local bandwidth to 1/10th normal (10 megabit per second as opposed to 100 megabits per second) however this won't directly affect such a low speed internet connection but it may cause the priority to change. when i use my pc for torrents and my psp for browsing at the same time its the psp that suffers the poorer speed so this is a possible option.
thirdly as mentioned qos should be able to do this - i have no experience using it so, again, google is your friend.
fourthly you might be able to mess with the internet settings to cripple the machines connection but this is trouble and can have other side effects, that's why this option is last.
my reccomendation is get some software to do it and make sure she uses it. this is by far the easiest, safest and quickest option.

(This post was last modified: 23/11/2007 07:18 PM by Anger.)