be the belle of the ball

Examples from literature

About these young belles gathered the densest throng of all the crowd. 
No belle ever kept her clothes in better order than these were. 
Philippa was, as heretofore, the belle, looking more than usually lovely in a light gossamer dress of white and pink. 
The fashionable belles and beauties were not even aware of her existence, being too entirely absorbed in their yearly husband-hunt to think of any one but themselves and their prey. 
You'll be the belle of the ball, Virginia.