Firstly it is a refurbished notebook and secondly 6GB is OTT for light usage. If your sister is not doing any sort of gaming I would go with a low end HD4*** graphics card as it has the improved UV2 media decoder as opposed to the earlier UVD in the HD3*** series.
I would also be looking to get Windows 7 too.
Also the newer Dell notebooks have LED backlights which are better
IIRC.
I would probably go for one of the Dell notebooks listed here:
http://www.dmxdimension.com/dell-uk/...codes-coupons/
The website I linked to lists the current Dell deals and the links are directly to the Dell website.