Here's a better suggestion (No, this is not a troll).
Considering your sister got NVidia, that means that your motherboard probably doesn't support ATI, so I did my best to find a good card for this.
Newegg.com - ECS NGT240-1GQR-F GeForce GT 240 1GB 128-bit DDR3 PCI Express 2.0 x16 HDCP Ready Video Card
Funny thing is, one person got an upgrade from that card your sister got. Also, this card about the same price, but more advanced. Tell your sister to return that one she has and pick this bad boy up.