The phrase "The belle of the ball" is often used to describe:

• Be the belle of the ball: [idiom]
English meaning: to be the most attractive woman at a party or similar event.
Bangla meaning: কোন পার্টিতে সবচেয়ে আকর্ষণীয় মহিলা।

Example: 
- She wore a dress of crimson silk to the dinner and was the belle of the ball.
- Even though it was her first formal event, Maria's elegance and charm made her the belle of the ball.

Correct answer: A person who is the center of attention at an event.

Source: Cambridge Dictionary.