Controlling Router?
 

Is it possible to control how much "speed" router gets?

My sister is downloading bunch of movies half of the time and I am lagging like madman while I am googling something.

Is it possible to control the speed that sister gets?

Your router probably has QoS (Quality of Service) controls. You can use them to set all sorts of traffic priority settings. For example, a lot of routers let you specify which IP to give low priority to. You can also do it by ehternet port, MAC Address, and so forth, depending on the router you're using.