None of the Nokia models below 10K would provide you a 3.2MP cam that your sis is already using. If she can compromise with a 2MP cam then a few models that can be looked at would be 5310 and 5320. N70 ME rules itself out on weight and thickness front. If you think about extending the budget...some very good phones would be E51, N73 and 5620.
BTW if you are thinking about k810i then you are already looking at something around 11K...why not spend just 500 bucks more and get a much cooler looking T700
