Youngji used to be a CCM trainee and she was really good at dancing... She has danced to song like Sherlock(shinee) Bang(after school) Bad Girl Good Girl(Miss A) And many more you will see proof in this links
Search this for more covers by her : link
and also the boys cover : link
In the show where they showed off charns and such she showed that she could dance to the songs (some of them)
In Weekly Idol there she danced to sherlock and warrior.
You could also search on google: Youngji dance.