Wangfujing shopping street is the most famous for visitors--nice environment, adjacency to the Tian'anmen Square and Forbidden City, clean street bars, and backstreet traditional snack bars, etc.
Xidan shopping area is most popular for the local youth. There are quite some modern shopping malls with comfortable shopping environment.
Qianmen and Dashilan shopping streets are China's traditional shopping streets located to the south of Tian'anmen Square, and boast significant traditional buildings and time-honoured brands.
Other famous shopping areas include Lufthansa Tower (expensive imported goods and cafes), Guomao (International Trading Center) Shopping mall (very nice and top-end), Shin Kong Shopping Mall (nice boutiques and cafes), etc;
There are also featured shopping areas such as Yabao Road and Silk Street (bargain garments), Panjiayuan (antiques), etc.
wish you and your wife a nice shopping experience in Beijing :-)