冰雪聪明... only for girls?
冰雪聪明 always describes that someone is very clever and smart. It comes from 唐·杜甫《送樊二十三侍御赴汉中判官》诗：“坐知七曜历，手画三军势。冰雪净聪明，雷霆走精锐。”. But 冰雪聪明 is not only for girl.
冰雪聪明 can be used to describe the child too----冰雪聪明的孩子, but be careful when you use it to describe adult, especially male adult.
Other examples in ancient articles:

以冰雪聪明的文章，写雷霆精锐的思想，这种议论，就容易动人听闻了。（清·曾朴《孽海花》第十回）
姬冰雪聪明，靡不淹悟，类多韜匿不言。(清·陈孟楷 《湘烟小录·香畹楼忆语》)

Source：
為何叫冰雪聰明