If she knows how, then yep. There are plenty of ways to monitor internet usage, sites visited, etc. Of course, you don't have to be the network admin to do all that, you just need sufficient priviledges.
If you mean without messing with anything on the users pc's, it depends on the type of router you have. With Cisco routers you can set link bandwidth speeds, set path choice, etc. which will affect your dl speeds.
So yes you can limit the dl speeds, but I'm thinkin you'd need the right hardware.
ok. a friend of mine decided to download this program and gets a kick out of going to a public network (my city has free unprotected wireless zones) and watching what people are doing. i was just wondering if there are any laws against this type of action? or as long as it is a public network, people are all taking that chance and accepting it?